On Fri, Aug 13, 2010 at 08:29:07AM -0400, Christoph Hellwig wrote:
> On Fri, Aug 13, 2010 at 12:35:44PM +0200, Michael Monnerie wrote:
> > On Freitag, 13. August 2010 Stan Hoeppner wrote:
> > > Some benchmark results maybe worth a look:
> > > http://btrfs.boxacle.net/repository/raid/2.6.35-rc5/2.6.35-rc5/
> > Thanks - it would have been great to see xfs with delaylog in that
> > comparison, but the graphs are very very nice.
> > XFS seems performing better the more threads there are, just in "large
> > file random reads" it's the slowest - why this?
> Any idea who is doing these runs?
IIRC the tests are run by someone from IBM, but I cannot remember
who it is.
> Once we figure out what that large
> file random reads loads is I'm sure we could fix it soon.
Random Reads (raid, single-disk)
Start with 1024 files.
100 MB files on the raid system.
35 MB files on the single-disk system.
Each thread reads a fixed amount of data from a random location in one
file using 4 kB reads.
5 MB reads on the raid system.
1 MB reads on the single-disk system.
So it's not a small random read workload (100GB data set), so the
files on XFS are probably more spread out over multiple AGs
and hence further apart than other filesystems. Hence a greater
average seek distance, hence it slower throughput....
> And asking
> him/her to add -o delaylog would also be good.
Yes, that would be an interesting comparison...