Sounds to me like something is wrong as on my 20 disk backup machine with 20 1TB disks on a single raidz2 vdev I get the following with DD on sequential reads/writes:
writes: r...@opensolaris: 11:36 AM :/data# dd bs=1M count=100000 if=/dev/zero of=./100gb.bin 100000+0 records in 100000+0 records out 104857600000 bytes (105 GB) copied, 233.257 s, 450 MB/s reads: r...@opensolaris: 11:44 AM :/data# dd bs=1M if=./100gb.bin of=/dev/null 100000+0 records in 100000+0 records out 104857600000 bytes (105 GB) copied, 131.051 s, 800 MB/s zpool iostat <pool> 10 gives me about the same values that DD gives me. Maybe you have a bad drive somewhere? Which areca controller are you using as maybe you can pull the smart info off the drives from a linux boot cd as some of the controllers support that. Could be a bad drive somewhere. On 06/18/2010 02:33 AM, Curtis E. Combs Jr. wrote: > Yea. I did bs sizes from 8 to 512k with counts from 256 on up. I just > added zeros to the count, to try to test performance for larger files. > I didn't notice any difference at all, either with the dtrace script > or zpool iostat. Thanks for you help, btw. > > On Fri, Jun 18, 2010 at 5:30 AM, Pasi Kärkkäinen <pa...@iki.fi> wrote: > >> On Fri, Jun 18, 2010 at 02:21:15AM -0700, artiepen wrote: >> >>> 40MB/sec is the best that it gets. Really, the average is 5. I see 4, 5, 2, >>> and 6 almost 10x as many times as I see 40MB/sec. It really only bumps up >>> to 40 very rarely. >>> >>> As far as random vs. sequential. Correct me if I'm wrong, but if I used dd >>> to make files from /dev/zero, wouldn't that be sequential? I measure with >>> zpool iostat 2 in another ssh session while making files of various sizes. >>> >>> >> Yep, dd will generate sequential IO. >> Did you specify blocksize for dd? (bs=1024k for example). >> >> As a default dd does 4 kB IOs.. which won't be very fast. >> >> -- Pasi >> >> >>> This is a test system. I'm wondering, now, if I should just reconfigure >>> with maybe 7 disks and add another spare. Seems to be the general consensus >>> that bigger raid pools = worse performance. I thought the opposite was >>> true... >>> -- >>> This message posted from opensolaris.org >>> _______________________________________________ >>> zfs-discuss mailing list >>> zfs-discuss@opensolaris.org >>> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss >>> >> > > > _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
