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. Thanks for any info, Steve Bergman -- 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
