On Thu, Jun 06, 2013 at 06:52:03PM -0500, Steve Bergman wrote: > I have a Dell T310 server set up with 4 Seagate ST2000NM0011 2TB > drives connected to the 4 onboard SATA (3Gbit/s) ports of the > motherboard. Each drive is capable of doing sequential writes at > 151MB/s and sequential reads at 204MB/s according to bonnie++. I've > done an installation of Scientific Linux 6.4 (RHEL 6.4) and let the > installer set up the RAID10 and logical volumes. What I got was a > RAID10 device with a 512K chunk size, and ext4 extended options of > stride=128 & stripe-width=256, with a filesystem block size of 4k. All > of this seems correct to me. > > But when I run bonnie++ on the array (with ext4 mounted > data=writeback,nobarrier) I get a sequential write speed of only > 160MB/s, and a sequential read speed of only 267MB/s. I've verified > that the drives' write caches are enabled. > > "sar -d" shows all 4 drives in operation, writing 80MB/s during the > sequential write phase, which agrees with the 160MB/s I'm seeing for > the whole array. (I haven't monitored the read test with sar.) > > Is this about what I should expect? I would have expected both read > and write speeds to be higher. As it stands, writes are barely any > faster than for a single drive. And reads are only ~30% faster. We have a wiki page on performance at https://raid.wiki.kernel.org/index.php/Performance >From the examples mentioned there you should be able to get something like 300 MB/s sequential write and 700 MB/s sequential read. Raid1 and raid10,near could slow down your sequential read considerable, while raid10,far and raid5 should give you read speed in the 700 MB/s range. Have a look at the bonnie results reported for a variation on chunk size etc. 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
