XFS: Abysmal write performance because of excessive seeking (allocation groups to blame?)

[Stan Hoeppner]

On 4/13/2012 2:36 PM, Stefan Ring wrote:
>> Let's rerun it with files cached (the machine has 16 GB RAM, so
>> every single file must be cached):
>>
>> # time tar xf test.tar
>>
>> real    0m50.842s
>> user    0m0.809s
>> sys     0m13.767s
> 
> That’s about the same time I’m getting on a fresh (non-fragmented)
> file system with the RAID 6 volume.
> 
> Interestingly, the P400’s successor, the P410 does recognize a setting
> that the P400 lacks, which is called elevatorsort. It sounds like this
> could make all the difference. Unfortunately, the P400 doesn’t have
> it. I don’t have a P410 with more than 2 drives to test this, but some
> effect should definitely be measurable.
> 
> Since this finding has piqued my interest again, I’m willing to invest
> a little more time, but I’m completely occupied for the next few days,
> so it will have to wait a while.

What configuration are you running right now Stefan?  You said you went
back to XFS due to the EXT4 lockups, but I can't recall what RAID config
you put underneath it this time.

-- 
Stan