[Dovecot] XFS vs EXT4 for mail storage

[Stan Hoeppner]

On 5/3/2013 4:34 AM, Alessio Cecchi wrote:
> Il 03/05/2013 10:48, Stan Hoeppner ha scritto:
>> On 5/2/2013 7:04 AM, Alessio Cecchi wrote:
>>
>>> "rw,noatime,attr2,delaylog,nobarrier,inode64,noquota"
>> ...
>>> and I'm running it on RHEL 6.4
>>
>> I assume this is from /proc/mounts?  All of those but for noatime,
>> nobarrier, and inode64 are defaults.  You've apparently specified these
>> in /etc/fstab.  noatime is useless as relatime is the default.  Google
>> "XFS relatime vs noatime".
>>
>> I assume you have a RAID controller or SAN head with [F|B]BWC and have
>> disabled individual drive write caches of array disks, given you've
>> disabled journal write barriers.  If drive caches are in fact enabled,
>> and/or you don't have [F|B]BWC, then journal write barriers need to be
>> enabled.  If not you're skydiving without a reserve chute.
>>
> 
> Thanks Stan, yes the output is from /proc/mounts.
> 
> We are running XFS on RAID controller but we havent disabled individual

Which RAID controller?  Does it have BBWC (battery backed write cache)?
 How much cache RAM?

> drive write caches. So what options suggest in fstab for XFS with non
> high-end RAID/SAN ?

Get rid of noatime and use the default, relatime.  Only specify
nobarrier if you have both:

1.  Working BBWC on your RAID card
2.  Individual disk drive caches are disabled
(and preferably a good UPS)

RAID BBWC is worthless if drive caches are still enabled.  This can
corrupt your filesystem if power fails, or the kernel crashes, because
writes to the journal may be lost.

-- 
Stan