i changed the order of the drives. Now sda/sdb are the boot drives (mirrored), sdc for full data and sdd for trend data.

Added four more disks to fb0 in order to speed up the copy process. As sda is a spare disk from alex this drive is not identical with sdb, so i don't know if we can create a mirror.
I think we should create the mirror with two identical drives in order to avoid problems. So i copied everything to sdb already and i will copy the content of sdb to the other four disks.
Two them we will keep as a backup, the other two will be the boot disks for the second RT system for peters lab.