Thanks for trying to help me! My problem is (looks like) solved. It was a kernel problem. (I think...) When I switch to 2.6.13-rc6 (from rc3), the problem is gone! It is very interesting! I use SWRAID to distribute equal load to nodes. (raid0 chunksize 32k) In my system with 2.6.13-rc3 the "node-3" gets much more (4x - 5x) read requests, but dont know why, dont ask! :-) First I think, the XFS's log is somehow always on 3 rd chunk. I send this question to XFS-list too, and get this answer: "The XFS log is always write, except recoverying." - Thats right! Next idea is to break more the 32k chunks, and send this previous letter to here. But I have more problems (network layer-bug) with 13-rc3, and try the newer kernel, and the problem is gone. :-) It looks like some network issue. Thanks Janos ----- Original Message ----- From: "Neil Brown" <neilb@xxxxxxxxxxxxxxx> To: <djani22@xxxxxxxxxxxxx> Cc: <linux-raid@xxxxxxxxxxxxxxx> Sent: Thursday, August 18, 2005 6:59 AM Subject: Re: perfomance question. > On Tuesday August 16, djani22@xxxxxxxxxxxxx wrote: > > Hello list, > > > > I have performance problem. (again) :-) > > > > What chunk size is better in raid5, and raid0? > > The lot of small chunks, or some bigger? > > This is highly dependant one workload and hardware performance. > The best thing to do is develop a test that simulates your real > workload and run it with various stripe sizes, and see which one wins. > > I suspect there would be very little gain in going to very small chunk > sizes (<16k). Anywhere between there and 1Meg is worth trying. > > mdadm uses a default of 64k which is probably not too bad for most > situations, but I cannot promise it being optimal for any. > > Sorry I cannot be more helpful. > > Your performance problem may not be chunk-size related. Maybe > increasing the readahead (with blockdev) would help... > > NeilBrown > - > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
