[Dovecot] Best filesystem?

[Stan Hoeppner]

Timo Sirainen put forth on 1/30/2011 4:40 PM:
> On Sun, 2011-01-30 at 16:13 -0600, Stan Hoeppner wrote:
>>>>> be, but it still gives you 0 byte files, so make sure you have a good UPS
> ..
>> "Q: Why do I see binary NULLS in some files after recovery when I unplugged the
>> power?
> 
> 0 byte files != NULL bytes in files. 

IIRC, the former is the current XFS (correct) behavior (which you quoted from an
old email, not today), and the latter is the behavior fixed by the 2007 patch.
The text in the FAQ can be a bit confusing as neither the before or after
behavior is thoroughly explained.

> My guess is it's the same problem
> as described in
> http://thunk.org/tytso/blog/2009/03/12/delayed-allocation-and-the-zero-length-file-problem/

Similar but not quite exactly the same.  For practical purposes, as seen by an
OP, they are functionally the same problem, so the exact cause is a bit
irrelevant from an OP's perspective.  XFS, along with all the journaling
filesystems, still "suffers" from this delayed allocation dilemma during power
loss/crash, as I've stated previously on this list.

If you want performance, there is a required sacrifice.  In this case, delayed
allocation gives the performance, but it sacrifices some "on disk" guarantees
WRT power loss or crash.  Again, this isn't the same issue as the XFS bug fixed
in 2007.  An XFS system today will still suffer data loss due to power
loss/crash if there is write data in the Linux buffer cache, which is the case
for all Linux journaling filesystems, not just XFS, as Ted T'so so eloquently
points out in his blog post.

-- 
Stan