[Dovecot] GFS (Was: dovecot Digest, Vol 93, Issue 41)

[Eric Rostetter]

Quoting Alan Brown <ajb2 at mssl.ucl.ac.uk>:

> I can't speak for OCFS2, but after several years' experience with  
> the filesystem I strongly recommend NOT using GFS/GFS2.

GFS2 works for me.  GFS was a bit slow, but GFS2 meets my (perhaps low)
needs.  Of course, my use case is different (e.g., I don't use it with
quotas, in fact I've stayed away from it anywhere I need quotas).

> Its locking model is incredibly slow (500 locks/second on a  
> filesystem mounted with quotas enabled and noatime) and results in  
> dire performance - plus

Did you raise plock_rate_limit from its defaults?  The defaults will
indeed suck.

> there's a known crash vulnerability if files are repeatedly renamed  
> in large directories (this bites us regularly...)

Never had that happen...  But then, my applications don't repeatedly
rename files in large directories (e.g., I don't use maildir) and I
don't use quotas on GFS.

> GFS2 isn't an "enterprise" filesystem by any stretch of the  
> imagination, despite what a number of enthusiastic salespeople might  
> try to convince you of. We're lucky to keep the GFS servers up for  
> more than a week at a time.

GFS isn't for all applications.  I've used it for 2 different applications
for which it has proven well suited.  Every discussion I've seen about
GFS has always said "don't use it with large directories of small files"
so if that is your use case, then you must be ignoring common wisdom...

Given the right use case (including dovecot with mbox and dovecot indexes)
it seems to work fine...  I've used it for another project also without
problems (been running for years now in both cases).

-- 
Eric Rostetter
The Department of Physics
The University of Texas at Austin

Go Longhorns!