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postgrey vs postscreen

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  • Postfix Support Mail
    I m currently running postgrey, but a recent thread here got me thinking about postscreen, which I hadn t considered before. What are the pros and cons of one
    Message 1 of 23 , May 1, 2012
      I'm currently running postgrey, but a recent thread here got me thinking
      about postscreen, which I hadn't considered before.

      What are the pros and cons of one versus the other? Are there advantages of
      one over the other for a given application?

      --Mac
    • karavelov@mail.bg
      ... They use different, complementing strategies to fight spam. We currently run both of them (postscreen, greylisting) with great success. Another greylisting
      Message 2 of 23 , May 1, 2012
        ----- Цитат от Postfix Support Mail (postfixsm@...), на 01.05.2012 в 22:14 -----

        > I'm currently running postgrey, but a recent thread here got me thinking
        > about postscreen, which I hadn't considered before.
        >
        > What are the pros and cons of one versus the other? Are there advantages of
        > one over the other for a given application?
        >
        > --Mac


        They use different, complementing strategies to fight spam. We currently run
        both of them (postscreen, greylisting) with great success.

        Another greylisting server that uses memcached as a backend and is written for
        postfix could be found here:
        https://github.com/luben/postfix-utils


        --
        Luben Karavelov
      • Noel Jones
        ... Please don t hijack threads. Start a new message instead of changing the subject of an existing message. Postgrey and postscreen do different things.
        Message 3 of 23 , May 1, 2012
          postfixsm@...:
          > I'm currently running postgrey, but a recent thread here got me thinking
          > about postscreen, which I hadn't considered before.
          >
          > What are the pros and cons of one versus the other? Are there advantages of
          > one over the other for a given application?
          >
          > --Mac

          Please don't hijack threads. Start a new message instead of
          changing the subject of an existing message.

          Postgrey and postscreen do different things. After you read up on
          them, you may want both.

          http://www.postfix.org/POSTSCREEN_README.html
          http://postgrey.schweikert.ch/



          -- Noel Jones
        • Postfix Support Mail
          Sorry about that. Reading the postscreen readme is what spawned the question. ## -----Original Message----- ## From: Noel Jones
          Message 4 of 23 , May 1, 2012
            Sorry about that.

            Reading the postscreen readme is what spawned the question.

            ## >> -----Original Message-----
            ## >> From: Noel Jones [mailto:njones@...]
            ## >> Sent: Tuesday, 01 May, 2012 12:29
            ## >> To: postfix users; postfixsm@...
            ## >> Subject: Re: postgrey vs postscreen
            ## >>
            ## >> postfixsm@...:
            ## >> > I'm currently running postgrey, but a recent thread here got me
            ## >> > thinking about postscreen, which I hadn't considered before.
            ## >> >
            ## >> > What are the pros and cons of one versus the other? Are there
            ## >> > advantages of one over the other for a given application?
            ## >> >
            ## >> > --Mac
            ## >>
            ## >> Please don't hijack threads. Start a new message instead
            ## >> of changing the subject of an existing message.
            ## >>
            ## >> Postgrey and postscreen do different things. After you
            ## >> read up on them, you may want both.
            ## >>
            ## >> http://www.postfix.org/POSTSCREEN_README.html
            ## >> http://postgrey.schweikert.ch/
            ## >>
            ## >>
            ## >>
            ## >> -- Noel Jones
          • Wietse Venema
            Michael Tokarev: [using unix instead of fifo ] ... The preferred pickup/qmgr IPC type (fifo or unix) can be a main.cf parameter setting (with an
            Message 5 of 23 , May 1, 2012
              Michael Tokarev:
              [using "unix" instead of "fifo"]
              > And yes, I verified the socket code (instead of pipe code) on linux
              > a few days ago and it appears to work fine there too. So indeed, this
              > is a very good possibility too, but it does not cover solaris well.

              The preferred pickup/qmgr IPC type (fifo or unix) can be a main.cf
              parameter setting (with an OS-dependent default value, e.g., fifo
              for Solaris and unix for everything else), and post-install can be
              updated to edit master.cf accordingly.

              This solves the "idle" mtime update problem a manner that is 100%
              maintainable. It involves adding one configuration parameter to
              main.cf, and adding a few lines to post-install that edit master.cf
              accordingly.

              > By default these dirs -- /var/spool/postfix/run/{pid,private,public} -
              > should be created at install time just like now these dirs are create
              > in /var/spool/postfix. The only change I'm asking about is to move
              > the "runtime" directories into a subdir (suggesting to name it "run"),
              > I don't ask to mount anything in there or to create these on boot.

              Sorry, that is not how Postfix is maintained.

              All aspects of Postfix are meant to be for general use, so that
              they are widely used, so that they can be routinely tested during
              development, so that they can be properly supported, and so that
              they don't break as Postfix evolves.

              Also, mounting stuff over Postfix directories breaks the basic model
              of how Postfix manages its files, and I definitely don't want some
              (Linux) distro maintainer to pick up on the idea. I have enough
              work on my hands to deal with damage control of (Linux) distro
              maintainers.

              [empty run directory]
              You seem to believe that Postfix IPC endpoints don't need to exist
              while Postfix is not running.

              > the mix -- pid, private, public -- the directories where the files
              > makes any sense at all till postfix is running _only_. Files in
              > there does not exist, so to say, when it is not running - even if
              > formally corresponding inodes do exist.

              That is incorrect.

              For example, the postdrop program will produce a warning message
              if the public/pickup node does not exist. By design this program
              MUST be able to run without errors while NO Postfix daemons are
              running. Normally, a missing public/pickup node is a sign of great
              trouble (mail would be queued forever) and it would therefore be
              wrong to shut up the error message.

              > [waiting for SSD to become a commodity product]

              An SSD has a write cycle limit of a million times or so. It should
              last forever with one mtime update per 5 minutes.

              Wietse
            • Michael Orlitzky
              ... If you enable the deep protocol tests, postscreen works pretty much like greylisting since it will 4xx any client that passes. When they reconnect, they
              Message 6 of 23 , May 1, 2012
                On 05/01/2012 03:42 PM, Postfix Support Mail wrote:
                > Sorry about that.
                >
                > Reading the postscreen readme is what spawned the question.
                >

                If you enable the deep protocol tests, postscreen works pretty much like
                greylisting since it will 4xx any client that passes. When they
                reconnect, they skip postscreen entirely; in effect, they've passed
                greylisting.

                Postgrey is a little more configurable (re: greylisting), and its
                introduction is less intrusive than switching will be. If you have to
                support older versions of postfix (sans postscreen), it also allows you
                to consolidate your configurations.

                On the other hand, I trust the postscreen code to be of the same
                quality as the rest of postfix. Postscreen does provide some additional
                anti-spam measures and reduces the load on your system. Finally, when
                all's said and done, you've got one less[1] moving part to worry about.

                Perhaps my favorite benefit is that with postscreen, we can afford the
                resources to use a pre-queue content filter. Now senders get a rejection
                if we e.g. detect a virus in their message. This greatly reduces the
                amount of time I have to spend on the phone.

                I would recommend switching eventually.


                [1] Technically there are probably more, but let's say "logical" moving
                parts.
              • Terry Barnum
                ... Mac, I made the switch to postscreen about week ago. I used http://www.postfix.org/postscreen.8.html and /dev/rob0 s guide at
                Message 7 of 23 , May 1, 2012
                  On May 1, 2012, at 12:14 PM, Postfix Support Mail wrote:

                  > I'm currently running postgrey, but a recent thread here got me thinking
                  > about postscreen, which I hadn't considered before.
                  >
                  > What are the pros and cons of one versus the other? Are there advantages of
                  > one over the other for a given application?
                  >
                  > --Mac

                  Mac,

                  I made the switch to postscreen about week ago. I used http://www.postfix.org/postscreen.8.html and /dev/rob0's guide at http://permalink.gmane.org/gmane.mail.postfix.user/218114 and also turned on deep protocol tests. I have not done any empirical testing here but my impression is that it works at least as well as postgrey. I like that it's seamlessly integrated into postfix.

                  -Terry
                • Robert Schetterer
                  ... depending on your setup, ( read postscreen readme.... ) you can combine them, specially if you use postgrey only selective which you should allready do yet
                  Message 8 of 23 , May 1, 2012
                    Am 01.05.2012 21:14, schrieb Postfix Support Mail:
                    > I'm currently running postgrey, but a recent thread here got me thinking
                    > about postscreen, which I hadn't considered before.
                    >
                    > What are the pros and cons of one versus the other? Are there advantages of
                    > one over the other for a given application?
                    >
                    > --Mac
                    >
                    >

                    depending on your setup, ( read postscreen readme.... )
                    you can combine them, specially if you use postgrey only selective
                    which you should allready do yet

                    --
                    Best Regards

                    MfG Robert Schetterer

                    Germany/Munich/Bavaria
                  • Michael Tokarev
                    ... Maybe this is something which don t really need any configuration parameters, just pick up whatever is best on current OS, from prior knowlege. But
                    Message 9 of 23 , May 2, 2012
                      02.05.2012 00:14, Wietse Venema wrote:
                      > Michael Tokarev:
                      > [using "unix" instead of "fifo"]
                      >> And yes, I verified the socket code (instead of pipe code) on linux
                      >> a few days ago and it appears to work fine there too. So indeed, this
                      >> is a very good possibility too, but it does not cover solaris well.
                      >
                      > The preferred pickup/qmgr IPC type (fifo or unix) can be a main.cf
                      > parameter setting (with an OS-dependent default value, e.g., fifo
                      > for Solaris and unix for everything else), and post-install can be
                      > updated to edit master.cf accordingly.

                      Maybe this is something which don't really need any configuration
                      parameters, just pick up whatever is best on current OS, from prior
                      knowlege. But indeed, config parameter there will do the job, and
                      will even let us test easily if things have changed on solaris,
                      without a need to recompile postfix.

                      I'm a bit afraid of possible questions this change may generate
                      in the future, when people will start asking "what it is for,
                      why can't it be hardcoded" etc. :)

                      > This solves the "idle" mtime update problem a manner that is 100%
                      > maintainable. It involves adding one configuration parameter to
                      > main.cf, and adding a few lines to post-install that edit master.cf
                      > accordingly.

                      Yes, it should solve the idle mtime update issue. Hopefully unix
                      sockets does not have this problem -- at least on linux, mtime on
                      these isn't updated on write.

                      >> By default these dirs -- /var/spool/postfix/run/{pid,private,public} -
                      >> should be created at install time just like now these dirs are create
                      >> in /var/spool/postfix. The only change I'm asking about is to move
                      >> the "runtime" directories into a subdir (suggesting to name it "run"),
                      >> I don't ask to mount anything in there or to create these on boot.
                      >
                      > Sorry, that is not how Postfix is maintained.
                      >
                      > All aspects of Postfix are meant to be for general use, so that
                      > they are widely used, so that they can be routinely tested during
                      > development, so that they can be properly supported, and so that
                      > they don't break as Postfix evolves.

                      Renaming directories does not break this. But see below...

                      > Also, mounting stuff over Postfix directories breaks the basic model
                      > of how Postfix manages its files, and I definitely don't want some
                      > (Linux) distro maintainer to pick up on the idea. I have enough
                      > work on my hands to deal with damage control of (Linux) distro
                      > maintainers.

                      Well, I already suggested this to Debian - to mount /var/spool/postfix/run
                      and change pid, private and public dirs to be symlinks into subdirs
                      in run/ -- exactly how I manage it locally for many years.

                      Switching to unix sockets should eliminate the need for this.
                      But yet again, see below...

                      > [empty run directory]
                      > You seem to believe that Postfix IPC endpoints don't need to exist
                      > while Postfix is not running.
                      >
                      >> the mix -- pid, private, public -- the directories where the files
                      >> makes any sense at all till postfix is running _only_. Files in
                      >> there does not exist, so to say, when it is not running - even if
                      >> formally corresponding inodes do exist.
                      >
                      > That is incorrect.
                      >
                      > For example, the postdrop program will produce a warning message
                      > if the public/pickup node does not exist. By design this program
                      > MUST be able to run without errors while NO Postfix daemons are
                      > running. Normally, a missing public/pickup node is a sign of great
                      > trouble (mail would be queued forever) and it would therefore be
                      > wrong to shut up the error message.

                      Aha. And that's exactly what I overlooked. I didn't knw that in
                      case public/pickup is not present, postdrop will complain loudly.
                      Indeed, this is a serious enough reason to rethink the whole idea.
                      So I'll hold on with the mentioned changes for debian, I definitely
                      don't want to break postfix in any way.

                      Besides, the same issue (missing pickup node) exists when postfix
                      has been installed but hasn't been run even once. That one appears
                      to be of much less severity.

                      So, to sum it all up, it looks like the best solution will be to
                      switch to unix sockets, either with a config parameter or without.
                      In any way, I'd pick saner per-OS defaults for this, with sockets
                      for everything but solaris which will continue using fifos.

                      Thanks,

                      /mjt
                    • Wietse Venema
                      ... $ postconf -d|wc -l 920 No-one has complained sofar. ... Thank you for making my worst nightmares come true. I will do my best to prevent this from
                      Message 10 of 23 , May 2, 2012
                        Michael Tokarev:
                        > > The preferred pickup/qmgr IPC type (fifo or unix) can be a main.cf
                        > > parameter setting (with an OS-dependent default value, e.g., fifo
                        > > for Solaris and unix for everything else), and post-install can be
                        > > updated to edit master.cf accordingly.
                        >
                        > Maybe this is something which don't really need any configuration
                        > parameters, just pick up whatever is best on current OS, from prior
                        > knowlege. But indeed, config parameter there will do the job, and
                        > will even let us test easily if things have changed on solaris,
                        > without a need to recompile postfix.
                        >
                        > I'm a bit afraid of possible questions this change may generate
                        > in the future, when people will start asking "what it is for,
                        > why can't it be hardcoded" etc. :)

                        $ postconf -d|wc -l
                        920

                        No-one has complained sofar.

                        > > Also, mounting stuff over Postfix directories breaks the basic model
                        > > of how Postfix manages its files, and I definitely don't want some
                        > > (Linux) distro maintainer to pick up on the idea. I have enough
                        > > work on my hands to deal with damage control of (Linux) distro
                        > > maintainers.
                        >
                        > Well, I already suggested this to Debian - to mount /var/spool/postfix/run

                        Thank you for making my worst nightmares come true. I will do
                        my best to prevent this from happening, and if I find out that
                        they do it anyway, then I will raise hell and it won't be pretty.

                        Wietse
                      • Stan Hoeppner
                        ... To who at Debian? Lamont Jones? Has he replied to your idiotic idea yet? ... All of this nonsense because one guy on the planet feels he can t simply use
                        Message 11 of 23 , May 3, 2012
                          On 5/2/2012 6:02 AM, Wietse Venema wrote:
                          > Michael Tokarev:
                          >>> The preferred pickup/qmgr IPC type (fifo or unix) can be a main.cf
                          >>> parameter setting (with an OS-dependent default value, e.g., fifo
                          >>> for Solaris and unix for everything else), and post-install can be
                          >>> updated to edit master.cf accordingly.
                          >>
                          >> Maybe this is something which don't really need any configuration
                          >> parameters, just pick up whatever is best on current OS, from prior
                          >> knowlege. But indeed, config parameter there will do the job, and
                          >> will even let us test easily if things have changed on solaris,
                          >> without a need to recompile postfix.
                          >>
                          >> I'm a bit afraid of possible questions this change may generate
                          >> in the future, when people will start asking "what it is for,
                          >> why can't it be hardcoded" etc. :)
                          >
                          > $ postconf -d|wc -l
                          > 920
                          >
                          > No-one has complained sofar.
                          >
                          >>> Also, mounting stuff over Postfix directories breaks the basic model
                          >>> of how Postfix manages its files, and I definitely don't want some
                          >>> (Linux) distro maintainer to pick up on the idea. I have enough
                          >>> work on my hands to deal with damage control of (Linux) distro
                          >>> maintainers.
                          >>
                          >> Well, I already suggested this to Debian - to mount /var/spool/postfix/run

                          To who at Debian? Lamont Jones? Has he replied to your idiotic idea yet?

                          > Thank you for making my worst nightmares come true. I will do
                          > my best to prevent this from happening, and if I find out that
                          > they do it anyway, then I will raise hell and it won't be pretty.

                          All of this nonsense because one guy on the planet feels he can't simply
                          use an MUA with submission like everyone else does, but demands he be
                          able to run an MTA on his damn desktop/laptop, and demands the default
                          MTA config allows him to do what he wants seamlessly, possibly to the
                          detriment of others, mainly the guy who wrote this MTA for your use in
                          the first place. At least that's my read of this thread.

                          --
                          Stan
                        • Viktor Dukhovni
                          ... Stan, please have the decency to not reflexively abuse others on this list, or otherwise leave. Michael, thanks for all your contributions over the years.
                          Message 12 of 23 , May 3, 2012
                            On Thu, May 03, 2012 at 08:16:33AM -0500, Stan Hoeppner wrote:

                            > Has he replied to your idiotic idea yet?

                            Stan, please have the decency to not reflexively abuse others on
                            this list, or otherwise leave.

                            Michael, thanks for all your contributions over the years.

                            The issue you raised here is a valid concern. It is however best
                            to avoid needless distribution-specific tweaks to Postfix, so it
                            would be best if issues are resolved on this list, rather than by
                            downstream maintainers, who may not always take all the consequences
                            into account. To pick on Debian for example, we have the Debian
                            OpenSSL random number fiasco...

                            --
                            Viktor.
                          • Michael Tokarev
                            On 03.05.2012 17:16, Stan Hoeppner wrote: [] ... Please refrain from using such words in public forum. Such usage makes you to be of that kind. ... Your read
                            Message 13 of 23 , May 3, 2012
                              On 03.05.2012 17:16, Stan Hoeppner wrote:
                              []
                              > To who at Debian? Lamont Jones? Has he replied to your idiotic idea yet?

                              Please refrain from using such words in public forum.
                              Such usage makes you to be of that kind.

                              >> Thank you for making my worst nightmares come true. I will do
                              >> my best to prevent this from happening, and if I find out that
                              >> they do it anyway, then I will raise hell and it won't be pretty.
                              >
                              > All of this nonsense because one guy on the planet feels he can't simply
                              > use an MUA with submission like everyone else does, but demands he be
                              > able to run an MTA on his damn desktop/laptop, and demands the default
                              > MTA config allows him to do what he wants seamlessly, possibly to the
                              > detriment of others, mainly the guy who wrote this MTA for your use in
                              > the first place. At least that's my read of this thread.

                              Your read is incorrect. World is much larger than your imagination.

                              Thanks,

                              /mjt
                            • Wietse Venema
                              I already thanked Michael for his contributions in private email. Michael, does editing master.cf and s/fifo/unix/ solve the mtime file system updates problem?
                              Message 14 of 23 , May 3, 2012
                                I already thanked Michael for his contributions in private email.

                                Michael, does editing master.cf and s/fifo/unix/ solve the mtime
                                file system updates problem? This is already supported by existing
                                code, works on Linux and *BSD, and I can make a config parameter
                                that makes this configurable with system-dependent defaults.

                                If so, then we can avoid controversial changes, such as support to
                                mount over a critical Postfix directory without Postfix's knowledge
                                of such things happening.

                                Wietse
                              • Stan Hoeppner
                                ... My apologies for allowing my passion to transform into abrasiveness. ... Please (re)explain the use case you have in mind. It seemed to me the changes
                                Message 15 of 23 , May 3, 2012
                                  On 5/3/2012 8:48 AM, Michael Tokarev wrote:
                                  > On 03.05.2012 17:16, Stan Hoeppner wrote:
                                  > []
                                  >> To who at Debian? Lamont Jones? Has he replied to your idiotic idea yet?
                                  >
                                  > Please refrain from using such words in public forum.
                                  > Such usage makes you to be of that kind.

                                  My apologies for allowing my passion to transform into abrasiveness.

                                  >>> Thank you for making my worst nightmares come true. I will do
                                  >>> my best to prevent this from happening, and if I find out that
                                  >>> they do it anyway, then I will raise hell and it won't be pretty.
                                  >>
                                  >> All of this nonsense because one guy on the planet feels he can't simply
                                  >> use an MUA with submission like everyone else does, but demands he be
                                  >> able to run an MTA on his damn desktop/laptop, and demands the default
                                  >> MTA config allows him to do what he wants seamlessly, possibly to the
                                  >> detriment of others, mainly the guy who wrote this MTA for your use in
                                  >> the first place. At least that's my read of this thread.
                                  >
                                  > Your read is incorrect. World is much larger than your imagination.

                                  Please (re)explain the use case you have in mind. It seemed to me the
                                  changes you're proposing will have a positive effect, immediately
                                  anyway, for only a very small subset of Postfix users, for a niche
                                  configuration.

                                  This request seems very similar to one made on the XFS list not all that
                                  long ago. A user with a home theater PC and a single large WD Green
                                  drive was irked that the drive wouldn't stay asleep for more than 30
                                  seconds. He debugged it himself, and found a long standing XFS behavior
                                  of accessing the journal or filesystem superblock every 30s IIRC. He
                                  said this wasn't necessary and pleaded with the devs to change this
                                  behavior, just so his HTPC drive could sleep. XFS was never intended
                                  for such a setup, this behavior existing since ~1994/95. The average
                                  XFS setup is a server with a dozen to a few hundred or more drives in
                                  hardware RAID running 24x7--no sleeping. An SGI employee mentioned just
                                  a couple of weeks ago working with a single XFS filesystem spaning 600
                                  drives in an IS16000 array. Not your average XFS drive count, but it is
                                  a typical large XFS configuration, and quite a contrast from a single
                                  drive HTPC server in a living room.

                                  IIRC a patch was eventually developed after many months, when it was
                                  determined there was likely no downside, and mainlined after much
                                  regression testing and tweaking. All for the benefit of very very few
                                  non-typical XFS users.

                                  Anyway, I see this as a similar case, and a similar waste of resources
                                  expended for the benefit of very few users, when there is nothing
                                  inherently "wrong" with the current Postfix implementation, as far as I
                                  understand the request. Maybe I simply don't fully understand the issue
                                  and the potential benefits yet.

                                  --
                                  Stan
                                • john
                                  I do not see where Stan was abusive. Abrasive maybe, but then sometimes bumps on logs need sanding down this would appear to be one of those occasions.
                                  Message 16 of 23 , May 3, 2012
                                    I do not see where Stan was abusive.
                                    Abrasive maybe, but then sometimes bumps on logs need sanding down this
                                    would appear to be one of those occasions.

                                    On 03/05/2012 11:29 AM, Stan Hoeppner wrote:
                                    > On 5/3/2012 8:48 AM, Michael Tokarev wrote:
                                    >> On 03.05.2012 17:16, Stan Hoeppner wrote:
                                    >> []
                                    >>> To who at Debian? Lamont Jones? Has he replied to your idiotic idea yet?
                                    >> Please refrain from using such words in public forum.
                                    >> Such usage makes you to be of that kind.
                                    > My apologies for allowing my passion to transform into abrasiveness.
                                    >
                                    >>>> Thank you for making my worst nightmares come true. I will do
                                    >>>> my best to prevent this from happening, and if I find out that
                                    >>>> they do it anyway, then I will raise hell and it won't be pretty.
                                    >>> All of this nonsense because one guy on the planet feels he can't simply
                                    >>> use an MUA with submission like everyone else does, but demands he be
                                    >>> able to run an MTA on his damn desktop/laptop, and demands the default
                                    >>> MTA config allows him to do what he wants seamlessly, possibly to the
                                    >>> detriment of others, mainly the guy who wrote this MTA for your use in
                                    >>> the first place. At least that's my read of this thread.
                                    >> Your read is incorrect. World is much larger than your imagination.
                                    > Please (re)explain the use case you have in mind. It seemed to me the
                                    > changes you're proposing will have a positive effect, immediately
                                    > anyway, for only a very small subset of Postfix users, for a niche
                                    > configuration.
                                    >
                                    > This request seems very similar to one made on the XFS list not all that
                                    > long ago. A user with a home theater PC and a single large WD Green
                                    > drive was irked that the drive wouldn't stay asleep for more than 30
                                    > seconds. He debugged it himself, and found a long standing XFS behavior
                                    > of accessing the journal or filesystem superblock every 30s IIRC. He
                                    > said this wasn't necessary and pleaded with the devs to change this
                                    > behavior, just so his HTPC drive could sleep. XFS was never intended
                                    > for such a setup, this behavior existing since ~1994/95. The average
                                    > XFS setup is a server with a dozen to a few hundred or more drives in
                                    > hardware RAID running 24x7--no sleeping. An SGI employee mentioned just
                                    > a couple of weeks ago working with a single XFS filesystem spaning 600
                                    > drives in an IS16000 array. Not your average XFS drive count, but it is
                                    > a typical large XFS configuration, and quite a contrast from a single
                                    > drive HTPC server in a living room.
                                    >
                                    > IIRC a patch was eventually developed after many months, when it was
                                    > determined there was likely no downside, and mainlined after much
                                    > regression testing and tweaking. All for the benefit of very very few
                                    > non-typical XFS users.
                                    >
                                    > Anyway, I see this as a similar case, and a similar waste of resources
                                    > expended for the benefit of very few users, when there is nothing
                                    > inherently "wrong" with the current Postfix implementation, as far as I
                                    > understand the request. Maybe I simply don't fully understand the issue
                                    > and the potential benefits yet.
                                    >
                                  • Stan Hoeppner
                                    On 5/3/2012 6:54 PM, Bill Cole wrote: ... This could be completely resolved by PXE/bootp and NFS mounted root filesystems, and save you $200-500/node in disk
                                    Message 17 of 23 , May 4, 2012
                                      On 5/3/2012 6:54 PM, Bill Cole wrote:
                                      ...
                                      > For many of these systems,
                                      > the OS resides on a mirrored pair of local disks which see very
                                      > infrequent writes because every filesystem with significant flux is
                                      > physically resident across the SAN. Spinning disks draw power. Anything
                                      > drawing power generates heat. Heat requires cooling. Cooling typically
                                      > requires more power than the devices it is compensating for. Cooling
                                      > also requires careful attention to the details of physical server
                                      > density and rack design and so on...

                                      This could be completely resolved by PXE/bootp and NFS mounted root
                                      filesystems, and save you $200-500/node in disk drive costs after
                                      spending $1000-2000 for the NFS server hardware, or nothing using a VM
                                      server. It would also save you substantial admin time by using
                                      templates for new node deployments. This diskless node methodology has
                                      been around for ~30 years.

                                      > A local mail submission and trivial outbound transport subsystem is a
                                      > normal feature of any Unix-like machine. To operate robustly, it needs a
                                      > queueing and retry mechanism. It is helpful for environments with power
                                      > and cooling concerns if a mechanical disk (or worse: a mirrored pair of
                                      > disks) isn't forced to spin up every time that mechanism activates.
                                      > Every little wattage savings is useful, and avoiding truly pointless
                                      > disk writes is never a bad thing.

                                      SSD is a perfect solution here, in cases of non netboot machines. And
                                      right now small SSDs are less expensive than their rusty disk
                                      counterparts. If one is truly concerned about spurious spin ups eating
                                      power and generating heat, I would think one would not go after the
                                      software stack in a piecemeal fashion to solve the problem. The MTA
                                      isn't the only software waking the disk. The kernel will write logs far
                                      more often in many/most situations.

                                      > Well, beyond the data center environment there is also a very widespread
                                      > deployment of Postfix as the legacy mail subsystem on MacOS personal
                                      > machines, where the mail flow is typically extremely low.
                                      ...
                                      > Ultimately the result is having to choose
                                      > between power management and timely delivery. If the periodic wakeups
                                      > didn't force a disk write, it would be less onerous to let master run in
                                      > its normal persistent mode for a lot of Postfix users (many of whom may
                                      > not even be aware that they are Postfix users.)

                                      This is only true if two things persist into the future:

                                      1. Postfix isn't modified in order to perform a power management role
                                      2. Laptops will forever have spinning rust storage

                                      Addressing the first point, should it be the responsibility of
                                      application software to directly address power management concerns? Or
                                      should this be left to the OS and hardware platform/BIOS?

                                      Addressing the 2nd, within a few years all new laptops will ship with
                                      SSD instead of SRD specifically to address battery run time
                                      issues. Many are shipping now with SSDs. All netbooks already do,
                                      smart phones use other flash types.

                                      > Whether it is actually worthwhile to make a change that is only
                                      > significant for people who are barely using Postfix isn't a judgment I
                                      > can make. It's obvious that Dr. Venema takes significantly more care
                                      > with his code than I can really relate to, so I don't really know what
                                      > effort a conceptually small change in Postfix really entails.

                                      Wietse will make his own decisions as he always has.

                                      I'm simply making the point that issues such as power/cooling,
                                      wake/sleep, etc should be addressed at the hardware platform/OS level,
                                      or system or network architecture level, at the application level,
                                      especially if the effort to implement it is more than trivial.

                                      This is especially true when any such coding effort may only produce
                                      very short term gains, as these issues are already being addressed and
                                      will be completely resolved by other means (SSD) in the near
                                      future, or have already been resolved by 30 year old
                                      technology/architecture methods (netboot/NFS), depending on the platform
                                      scenario.

                                      --
                                      Stan
                                    • Bill Cole
                                      ... Yes, it is possible to fundamentally re-architect working environments that have been organically developed over years by adding significant new
                                      Message 18 of 23 , May 4, 2012
                                        On 4 May 2012, at 17:00, Stan Hoeppner wrote:

                                        > On 5/3/2012 6:54 PM, Bill Cole wrote:
                                        > ...
                                        >> For many of these systems,
                                        >> the OS resides on a mirrored pair of local disks which see very
                                        >> infrequent writes because every filesystem with significant flux is
                                        >> physically resident across the SAN. Spinning disks draw power.
                                        >> Anything
                                        >> drawing power generates heat. Heat requires cooling. Cooling
                                        >> typically
                                        >> requires more power than the devices it is compensating for. Cooling
                                        >> also requires careful attention to the details of physical server
                                        >> density and rack design and so on...
                                        >
                                        > This could be completely resolved by PXE/bootp and NFS mounted root
                                        > filesystems, and save you $200-500/node in disk drive costs after
                                        > spending $1000-2000 for the NFS server hardware, or nothing using a VM
                                        > server. It would also save you substantial admin time by using
                                        > templates for new node deployments. This diskless node methodology
                                        > has
                                        > been around for ~30 years.

                                        Yes, it is possible to fundamentally re-architect working environments
                                        that have been "organically" developed over years by adding significant
                                        new infrastructure to save on capital costs of hypothetical growth and
                                        maybe on future admin time. The idea that a server in the $1000-$2000
                                        range would be part of a global conversion to diskless servers or even
                                        the largest capital cost of such a project reveals that I failed to
                                        communicate an accurate understanding of the environment, but that's not
                                        terribly important. There's no shortage of well-informed well-developed
                                        specific proposals for comprehensive infrastructure overhaul, and in the
                                        interim between now and the distant never when one of those meets up
                                        with a winning lottery ticket and an unutilized skilled head or three, I
                                        have sufficient workarounds in place.

                                        I didn't mention that environment seeking a solution, but rather to
                                        point out that there are real-world systems that take advantage of the
                                        power management capabilities of modern disks and have nothing else in
                                        common with the average personal system. I think that was responsive to
                                        the paragraph of yours that I originally quoted. It's easy to come up
                                        with flippant advice for others to spend time and money to replace
                                        stable working systems, but it is also irrelevant and a bit rude.

                                        [...]
                                        >> Ultimately the result is having to choose
                                        >> between power management and timely delivery. If the periodic wakeups
                                        >> didn't force a disk write, it would be less onerous to let master run
                                        >> in
                                        >> its normal persistent mode for a lot of Postfix users (many of whom
                                        >> may
                                        >> not even be aware that they are Postfix users.)
                                        >
                                        > This is only true if two things persist into the future:
                                        >
                                        > 1. Postfix isn't modified in order to perform a power management role

                                        No reason for it to "perform" but it would be nice for it to "stop
                                        thwarting."

                                        > 2. Laptops will forever have spinning rust storage

                                        Who said anything about laptops?

                                        > Addressing the first point, should it be the responsibility of
                                        > application software to directly address power management concerns?
                                        > Or
                                        > should this be left to the OS and hardware platform/BIOS?

                                        Applications should not do things that are actively hostile to
                                        housekeeping functions of lower-level software (in this case: drive
                                        firmware) without a functional justification. It's not wrong for a
                                        filesystem to change the mtime on a pipe with every write to it, nor is
                                        it wrong for a filesystem to commit every change in a timely manner.
                                        This is not really fixable at a lower level without eliminating the
                                        hardware in question or making changes to filesystem software that could
                                        cause wide-ranging problems with other software.

                                        > Addressing the 2nd, within a few years all new laptops will ship with
                                        > SSD instead of SRD specifically to address battery run time
                                        > issues. Many are shipping now with SSDs. All netbooks already do,
                                        > smart phones use other flash types.

                                        This is not about laptops. Really.

                                        Systems can live a long time without drive replacements. Spinning rust
                                        with power management firmware is not going to be rare in running
                                        systems until at least 5 years after dependable & fast SSD's hit $1/GB
                                        for devices larger than 100GB. Of course, those drives may die out a lot
                                        faster where applications do periodic pointless writes that keep them
                                        running continuously.

                                        Note that the reason this issue exists *AT ALL* is to work around a bug
                                        in Solaris 2.4. I spent most of the last 14 years working mostly on
                                        Solaris systems in change-averse places and the last time I saw Solaris
                                        2.4 was 1999. I don't have the details of the bug or the free time to
                                        rig up a test system to prove it gone in whatever version Postfix needs
                                        to work on today, but I have no gripe with that relatively ancient and
                                        *likely* inoperative history being the blocking issue. I hope someone
                                        else can settle the issue. An argument that time will soon make this fix
                                        pointless is a bit ironic.


                                        >> Whether it is actually worthwhile to make a change that is only
                                        >> significant for people who are barely using Postfix isn't a judgment
                                        >> I
                                        >> can make. It's obvious that Dr. Venema takes significantly more care
                                        >> with his code than I can really relate to, so I don't really know
                                        >> what
                                        >> effort a conceptually small change in Postfix really entails.
                                        >
                                        > Wietse will make his own decisions as he always has.
                                        >
                                        > I'm simply making the point that issues such as power/cooling,
                                        > wake/sleep, etc should be addressed at the hardware platform/OS level,
                                        > or system or network architecture level, at the application level,
                                        > especially if the effort to implement it is more than trivial.

                                        See his discussion of the details. The code exists, what remains is the
                                        harder work of testing and getting all the defaults right.


                                        P.S.: Note that I have respected with your Reply-To header. Please
                                        return that courtesy.
                                      • Reindl Harald
                                        ... but only if you do not permanently spin them up and down power managment is the dead of a drive i have here disks with 35.000 uptime you can be sure with
                                        Message 19 of 23 , May 4, 2012
                                          Am 05.05.2012 03:05, schrieb Bill Cole:
                                          > Systems can live a long time without drive replacements.

                                          but only if you do not permanently spin them up and down
                                          power managment is the dead of a drive

                                          i have here disks with > 35.000 uptime
                                          you can be sure with "power-managment" they
                                          would still be dead

                                          try it out: spin down a drive running some years
                                          and you have a real good change that the next
                                          spin up is the final one

                                          > Spinning rust with power management firmware is not going
                                          > to be rare in running systems until at least 5 years

                                          and should be the first to get disabled in the real world

                                          the power you save in spin down a disk is meaningless
                                          in any way, the power for produce a new drive because yours
                                          died by permanently spin up/down is much higher and the cost
                                          of the new drive also compared with let the drive run
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