I use a Dell PE1800 with CERC 1.5/6ch SATA controller (it's a Adaptec
2610SA)and SATA-drives with Raid 5 & run on OES SP2

NSS-Volume on Raid 5 array (/dev/sdb)

dmesg shows:
aacraid-driver 1.1-4 dec 13 2005
AAC0: kernel, bios, monitor 4.1-0 [7417]
SCSI device sdb: drive cache: write through

- CERC BIOS controller cache is set to write back! but
aacraid-driver reports write through !!!

- if a windows-client has write activities on this volume, then there is
a massive delay for all other clients

- read performance on this volume is very good (Raid 5)

It seems to be a problem with the aacraid-driver write actions ...
DELL only support RedHat and SLES9-64bit ...

I read about some aacraid problems (earlier thread here and in
communities) with kernel 2.6 & some problems solved with kernel 2.6.11, but
OES SP1 has 2.6.5-7.201
OES SP2 has 2.6.5-7.244

Any ideas ?