[Gluster-users] XFS and MD RAID

[Brian Candler]

On Wed, Aug 29, 2012 at 04:34:32PM +0200, s19n wrote:
> Randomly found on Google:
> 
> http://www.jive.nl/nexpres/doku.php?id=nexpres:nexpres_wp8#tests_on_xfs_file_system
> 
> "It is our opinion that the normalization of XFS behavior on a 24 disks
> array is due to some proprietary round-robin algorithm on the raid card
> that caused during the tests on a 12 disks array a 'missing disk' signal
> that slowed down the pace, even though some downfalls on the 24 disks
> array still happen every 18/20 files written. We ought to say that the
> downfall pattern is not related to time delays or file sizes, but it is
> instead a peculiarity of the XFS file system."
> 
>  Now I'd _really_ like to know if you are using a Megaraid or, as you say
> at the end, a mpt2sas controller/driver, because I am going to setup a
> new gluster volume with them, and considering this issue and the ext4
> one I don't really know what to choose...

It's mpt2sas. I'm afraid I don't understand what exactly they are trying so
say, beyond perhaps some unexpected reduction in write performance.

It wouldn't concern me unduly unless my application was heavily
write-intensive with the same pattern of writes as the benchmark was
testing (and there is scant description of this)

Regards,

Brian.