On Tue, Mar 25, 2008 at 01:22:03PM +0000, Peter Grandi wrote: > >>>> I have a 4 drive array with 1 TB Hitachi disks, formatted > >>>> as raid10,f2 I had some strange observations: 1. while > >>>> resyncing I could get the raid to give me about 320 MB/s in > >>>> sequential read, which was good. After resync had been > >>>> done, and with all 4 drives active, I only get 115 MB/s. > > [ ... ] > > >> Is this with, or without, your patch to avoid "read-balancing" > >> for raid10/far layouts? It sounds like it is without that > >> patch ???? > > > I tried both without the patch and with the patch, with almost > > same resulte. > > That could be the usual issue with apparent pauses in the stream > of IO requests to the array component devices, with the usual > workaround of trying 'blockdev --setra 65536 /dev/mdN' and see if > sequential reads improve. Yes, that did it! > > Is resync building some table, and could that be it? Or could > > it be some time of inode traffic? > > One good way to see what is actually happening is to use either > 'watch iostat -k 1 2' and look at the load on the individual MD > array component devices, or use 'sysctl vm/block_dump=1' and look > at the addresses being read or written. Good advice. I added your info to the wiki. best regards keld -- 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
