disk order problem in a raid 10 array

Hello

trying to solve my problem with a unusable raid10 array, I discovered that 
disk order is mixed between each boot - even with live-cd.
Here's an extract from dmesg:
[   12.5]  sda:
[   12.5]  sdc:
[   12.5]  sdd:
[   12.5]  sde: sdd1
[   12.5]  sdf: sdc1
[   12.5]  sda1 sda2
[   12.5]  sdg: sde1
[   12.5]  sdf1

is that normal?
could this be a sign of hardware controler problem?
could this happen because all disks are sata-3 except 1 SSD which is sata-2?


Xavier
xavier@alternatif.org