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RE: postgrey vs postscreen

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  • 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 1 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 2 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 3 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 4 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 5 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 6 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 7 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 8 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 9 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 10 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 11 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 12 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 13 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 14 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 15 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 16 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 17 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 18 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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