It doesn't really matter what chunk sizes I set, but, for example, I create three RAID5's of 5 drives each with a chunk size of 32K, and create a RAID0 comprised of the three RAID5's with a chunk size of 64K: md0 : active raid0 md27[2] md26[1] md25[0] 1885098048 blocks super 1.2 64k chunks If I write to one of the RAID5's, using: # dd of=/dev/md27 if=/dev/zero bs=1024k oflag=direct ... then "iostat -dmx 2" shows the drives being written to in 32K chunks (avgrq-sz=64), as you'd expect. But, writing to the RAID0 that's striping the RAID5's, shows everything being written in 4KB chunks (iostat shows avgrq-sz=8) to the RAID0 as well as to the RAID5's. Why is that? Note that this is true for reading too. Note I don't see the same problem when using RAID10 (via striped RAID1's) or RAID100 (via striped RAID10's). ... this is on SLES11 using a 2.6.32.43-0.5 kernel. Thanks, Chris -- 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
