On Mon, Feb 09, 2009 at 09:27:28PM +0100, Piergiorgio Sartor wrote: > Hi all. > > I've setup a system with two RAID volumes. > One is a small RAID-1, /dev/md0, with the /boot > content, the other is a RAID-10 f2, with LVM, > for the rest of the system. > > I just noticed that /dev/sdb, which is not the > boot disk, I assume, has more reads than /dev/sda. > Writes are the same, here is the output of "iostat": > > Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn > sda 10.08 183.15 408.74 755018 1684972 > sda1 0.04 1.24 0.02 5118 66 > sda2 10.03 181.71 408.72 749071 1684880 > sdb 10.49 187.64 408.74 773532 1684972 > sdb1 0.03 1.17 0.02 4837 66 > sdb2 10.44 186.26 408.72 767832 1684880 > md1 62.95 367.26 391.79 1513976 1615112 > md0 0.02 0.18 0.00 724 8 > > Note that sda1 has more reads than sdb1. > This is possibly due to the fact that it is > used during boot. > > What is strange, is sdb2, which has by far > more reads than sda2. Both belong to /dev/md1. > > Note also the /dev/sdb is the slowest of the > two drives. > > Is that somehow normal? > If not, is it possible to find out what or > why the reads are unbalanced? What kernel are you using? Before 2.6.25 you could have differences in usage. Anyway, I think the difference is too small to be of inportance for the performance. Or did you notice a difference? 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
