Nick Edwards wrote:
xfs is not very nice to you if you lose power, it's not as bad as it used to
be, but it still gives you 0 byte files,
I began to worry about this after that other thread showed XFS's
considerable strengths, and this one weakness. Co-incidentally,we had
already just built a couple of XFS servers in raid1 configurations
(the second is purely an rdiff-backup server for the first, and both
are raid1).
Because our work is frequently the subject of very close legal
scrutiny, we're utterly paranoid about losing email - that's why we've
created those two redundant servers.
I remember Stan (in the other thread) saying, also, that write-delays
due to caching were more or less built-in to the kernel anyway, so XFS
may not be alone in this problem. What I am not (yet) sure about, is
whether XFS is any 'more' vulnerable than others, or is any 'more'
catastrophically damaged, than others, due to power fail. Has any
analysis of this been published?
However, like the OP, our scale is quite small and this (potentially)
gives us one advantage over those very large users. We could forgo
some 'performance' if there were options in XFS that could reduce its
'vulnerability'. I looked at the XFS FAQ, and several of the archived
messages on the XFS list, but could not see any create options, or
mount options, that would reduce or inhibit the 'vulnerability window'
(but I'm no expert on filesystems, or the kernel, so maybe I didn't
understand what the FAQ was telling me). Would appreciate any
suggestions from those who use and know XFS.
so make sure you have a good UPS to
issue a safe shutdown of the server,
We are very susceptible to power outages, duration anything from 12
seconds to 14 hours (we're not in a city) and never notified in
advance. We use APC desktop UPS for workstations and the few servers
we have, and we then shut down. For security, the shutdown needs to
be automatic so that it takes effect if the site is unmanned -
overnight, for example.
'Absolutely secure email' needs the speed of XFS, the performance of
XFS on multitudes of small files, and the fault-tolerance of
some kind of non-volatile storage coupled with positive confirmation
of successful writes. One day, maybe.
Until then, email needs UPSs, it seems.
regards, Ron
