[ZODB-Dev] free space for FileStorage, and possible issues with repozo (was: Missing Content)

[Marius Gedminas]

On Sat, Jan 30, 2010 at 12:52:30PM -0500, Jim Fulton wrote:
> On Sat, Jan 30, 2010 at 6:18 AM, grahamperrin <G.J.Perrin at bton.ac.uk> wrote:
> > Michael Havard wrote:
> > >
> > > We're missing 16 days worth of content.
> > >
> > > Python 2.3.5, Zope 2.8.4, Plone 2.1.2, and a host of other products. ZEO
> > > configuration. Persistent disk caching is on.
> > >
> > > Yesterday everything was fine. All the content was there and accessible.
> >
> > I recall reading about a case that involved quietly running out of free
> > space on the volume used for FileStorage. Something like … the most recent
> > content was in RAM — and the running ZEO cluster seemed to work fine with
> > that (no adverse effect on the end user, at the time) — but that content
> > was not committed to disk (and so, was probably unrecoverable
> > following a restart of the OS).
> 
> If you remove an open file storage (on a Unix-like system), the file
> still exists, but it is no longer accessible from the original
> directory. New transactions are committed to this still existing file,
> not ram.

It is also possible to resurrect the deleted file as long as the process
keeping it open doesn't quit:

  1. find the pid and fd with lsof
  2. cat /proc/$pid/fd/$fd > /new/path

(sadly, ln doesn't seem to work -- "Invalid cross-device link" -- so you
need twice as much disk space)

Marius Gedminas
-- 
Only great masters of style can succeed in being obtuse.
                -- Oscar Wilde

Most UNIX programmers are great masters of style.
                -- The Unnamed Usenetter
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