On Wed, Jun 6, 2012 at 6:05 PM, Igor M Podlesny <for.poige+lsr@xxxxxxxxx> wrote: > On 6 June 2012 22:11, Ole Tange <ole@xxxxxxxx> wrote: >> On Tue, Jun 5, 2012 at 1:14 AM, Ole Tange <ole@xxxxxxxx> wrote: > […] >> If the bottleneck is md0_raid6, choose a chunk size that gives >> reasonable performance on your CPU (which in your case seem to be >> 32-64 KB). > > Which you're to never-ever do, since it's simply stupid to involve > bunch of disks into so brief I/O ops. Currently it seems the bottleneck is md0_raid6 running on one core as it seems can only deliver 400 MB/s to a 24 disk RAID6. The hardware + drivers supports 2000 MB/s according to the tests. So without change the total bandwidth is 400 MB/s. Let us say that we can change the config so md0_raid6 can deliver 600 MB/s, but at the cost that the hardware + drivers lose 2/3 of their performance and thus can only deliver 650 MB/s. Then the total bandwidth will be 600 MB/s. To me what matters is the total performance, so I would choose the 600 MB/s over the 400 MB/s any day. So Igor: Do you have numbers that back up your claim? Or do you advice against it just because "it's simply stupid"? /Ole -- 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
