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Re: [nslu2-linux] SlugOS 5.3: /var/volatile same as ramfs?

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  • Mike Westerhof (mwester)
    ... Unnecessary with recent SlugOS releases, including 5.3-beta. ... Yes. The major difference is that the volatiles mechanism is managed by a startup
    Message 1 of 3 , Jun 25, 2009
      Jan wrote:
      > Bump :)
      > -----Original Message-----
      > From: nslu2-linux@yahoogroups.com [mailto:nslu2-linux@yahoogroups.com] On
      > Behalf Of obi_jan
      > Sent: Tuesday, June 09, 2009 2:32 PM
      > To: nslu2-linux@yahoogroups.com
      > Subject: [nslu2-linux] SlugOS 5.3: /var/volatile same as ramfs?
      > As previously mentioned, I just advanced from SlugOS 3.10 to 5.3 and am
      > exploring this new world. Being a creature of habit, I immediately started
      > setting it up the same way I did under 3.10. In that regard, I always used
      > to apply the method to move /dev and /var to a ramfs, as described further
      > down in this Wiki article here:
      > http://www.nslu2-linux.org/wiki/FAQ/SpinDownUSBHarddisks

      Unnecessary with recent SlugOS releases, including 5.3-beta.

      > The rationale behind this is to minimize the writes to the memstick I am
      > booting off. However, I realized that in 5.3, most sub directories in the
      > /var tree actually reside in /var/volatile (sym-linked). After further
      > reading online and in this forum, I have come to the conclusion that
      > /var/volatile is in fact already an in-memory filesystem, is that correct?

      Yes. The major difference is that the "volatiles" mechanism is managed
      by a startup script and a config directory. This allows fine-grained
      control over what is in RAM, vs what is persistent. Read the comments
      in the "volatiles" file in /etc/default/ for details for your
      configuration. (The configuration is selected based on how you did the
      "turnup" command (turnup memstick vs turnup disk, for example) -- in
      addition to selecting a different syslogd configuration, turnup also
      selects different volatiles configurations.)

      > How much memory does it take away from the RAM, and do I now need to employ
      > log rotation and archiving strategies to make sure the volatile fs never
      > fills up?

      How much RAM it takes depends solely on how much you store in the
      filesystem, but it will not exceed 1/2 of the physical memory available
      (which works out to 16MB on an unmodified slug). It is commonly abuse
      of the /tmp directory that will fill up the space, so it is not usually
      necessary to rotate logs and all that. But feel free to do so if you wish.

      > Also, is it still worthwhile to try to move /dev to a separate ramfs to
      > further minimize access to it? I guess it's not necessary, as the access to
      > /dev is mostly read-only, which is not a problem for solid state memory, is
      > that correct?

      Correct. And it will be cached in any case, so unlikely to cause any
      real concern.

      > Under 3.10, I was actually booting off an external HDD, so it
      > was important for me to minimize both reads and writes to it to allow for it
      > to spin down after some idle time.

      I'm glad you won't be going down that path any longer; spindown of HDDs
      is a bad solution to whatever it is the real problem might be, and in
      the end it solves nothing. If you cannot live with a spinning HD, then
      a solid-state device (USB memory stick or even an SSD) is the better
      choice. :)

      -Mike (mwester)
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