Re: [HEADS-UP] Rawhide: /tmp is now on tmpfs (original) (raw)

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From: Pádraig Brady
Subject: Re: [HEADS-UP] Rawhide: /tmp is now on tmpfs
Date: Thu, 13 Sep 2012 01:56:41 +0100
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On 06/01/2012 02:05 PM, Pádraig Brady wrote:

It seems like we should default to /var/tmp in sort(1) and tac(1), as debian and fedora at least are probably moving to tmpfs for /tmp. I'll monitor the situation a bit before making the change.

Thinking a bit more about this, as I see it:

/tmp = stateless /var/tmp = stateful

What is actually used to back those paths is system specific and inconsequential to sort. sort logically just needs stateless storage, as after sort exits, its tmp files are no longer useful. If sort could restart operations then that would be a different story.

So sort should stick to /tmp I think, and not worry about system implementation details.

As an aside on tech for backing those paths: Ideally, tmpfs could be used for /tmp even for large files as swap could be used as needed. This swap could even be over nfs/nbd for nodes without stateful storage. If the swap (over net) implementation isn't up to scratch, then as a pragmatic solution one might need to configure paths considering 'size' as well as 'statefulness' and have /large_tmp which is backed by a traditional file system on disk and auto cleaned on boot. Disadvantages of that are:

  1. require boot cleanup scripts
  2. traditional file system on disk doesn't take advantage of the fact that we don't need to persist the data to disk/flash/net (which can be slower and less reliable). Traditional disk backed /tmp avoids possible swap issues with large files, but suffers from the above 2 disadvantages.

Another pertinent piece of info is that Debian have reverted the default setting of tmpfs backed /tmp: http://packages.debian.org/changelogs/pool/main/s/sysvinit/current/changelog#version2.88dsf-26

cheers, Pádraig.