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From Vincent Lefevre <vincent-...@vinc17.net>
Subject Re: Support for filesystem snapshots (?)
Date Tue, 03 Aug 2010 15:53:52 GMT
On 2010-08-03 08:03:33 -0500, Les Mikesell wrote:
> A filesystem snapshot should present exactly the same scenario as a
> machine that lost power or crashed for some similar reason at that
> moment, so the question boils down to whether subversion can recover
> sensibly from a crash at any point.

Not exactly: in case of a power loss or a kernel crash, the file
system can become inconsistent. I think you mean something like:
[...] that lost power or crashed while it wasn't writing to the
disk.

> The fsync's are going to be the critical thing for ordering
> operations at the disk level, however there is no guarantee how much
> of the fsync operation might have completed when a crash or snapshot
> happens.

It depends on whether the filesystem snapshot software takes kernel
buffers into account or not. And one can assume that the snapshot
isn't taken in the middle of a fsync.

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <http://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / Arénaire project (LIP, ENS-Lyon)

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