RAID-10 unbalanced reads

[Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>]

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?

Thanks a lot in advance,

bye,

-- 

piergiorgio