Re: Linux filesystems was [Re: Debian cd supporting ext4.]
Rob Owens put forth on 7/27/2010 4:36 PM:
> On Tue, Jul 27, 2010 at 01:39:18PM -0500, Stan Hoeppner wrote:
>> Volkan YAZICI put forth on 7/27/2010 12:19 PM:
>>
>>> About a year ago, in a similar rush to yours, I ported two of our
>>> PostgreSQL database servers to XFS. During testing period, I even
>>> couldn't *recover* the / fs after the very first power failure test.
>>
>> What write operations were you performing at the time you pulled the plug?
>> Unless you were writing the superblock it'd be almost impossible to hose the
>> filesystem to the point it couldn't mount. Were you doing a resize operation
>> when you pulled the plug? xfs_growfs? As far as recovery, it's automatic
>> upon mounting the XFS filesystem. What do you mean, precisely, by "couldn't
>> *recover* the / fs"?
>>
> Some anecdotal evidence in support of ext3's resilience to power loss:
>
> I recently lost power while my system was running. When power was
> restored, an fsck was automatically performed. During that fsck, I lost
> power again! I thought for sure I'd be hosed, but after the power came
> back and an fsck completed, everything seems to be working normally.
If no writes are in process or pending, it really doesn't matter which fs you
use, as none of them will suffer negative effects. All will recover after a
journal replay or fsck. For journaling filesystems that are configured
properly, even if a write is in progress when the power goes out, the
filesystem will not be corrupted as a result. You will have lost data, but
the filesystem itself will be healthy. This is one of the two main purposes
of a journaling filesystem. The other is rapid recovery. You experienced
both in your example. :)
--
Stan
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