Hi,

yes cache is enabled on controller and WB on luns.

hdparm report:
*-----------------------------------------------------------------------------*
hdparm -t /dev/sda
*-----------------------------------------------------------------------------*
/dev/sda:
Timing buffered disk reads: 56 MB in 3.06 seconds = 18.27 MB/sec
*-----------------------------------------------------------------------------*
hdparm -t /dev/sdb
*-----------------------------------------------------------------------------*
/dev/sdb:
Timing buffered disk reads: 408 MB in 3.00 seconds = 135.88 MB/sec
*-----------------------------------------------------------------------------*
hdparm -t /dev/sdc
*-----------------------------------------------------------------------------*
/dev/sdc:
Timing buffered disk reads: 128 MB in 3.04 seconds = 42.16 MB/sec
*-----------------------------------------------------------------------------*
hdparm -t /dev/sdd
*-----------------------------------------------------------------------------*
/dev/sdd:
Timing buffered disk reads: 98 MB in 3.00 seconds = 32.64 MB/sec

On another testmachine with only softwareraid 5 and older harddisks, i got this hdparm:
/dev/md0:
Timing buffered disk reads: 512 MB in 3.00 seconds = 170.47 MB/sec