Need help with Raid 5 Speeds

[ic3m4n2005]

Ok here are my specs:

Controller: Adaptec 31205, 256MB Ram onboard, 12 Ports
HDDs: 4x Samsung T166 in Raid 5
Clustersize: 64k
Usage: mainly as Filestorage with MP3s and Videos.

Problem is i get only about 80 mb per sec write speed, it should be more or am i wrong ?

[XS Janus]

Do you have write-back caching enabled on the controller.
It will make a tremendous difference.
Also 80MB/s in what direction: other drive to the array, or copying the file from the array to the array
80MB/s doesn't sound all THAT bad to me...
These are my results with 4xWD1000FYPS GreenPower drives. LINK (http://www.xtremesystems.org/forums/showpost.php?p=2967458&postcount=137)

My real life file transfer results with different stripe sizes:
Write results from other drive to the array are capped to 83.5 MB/s by the single 150GB Raptor from where the file was copied

[ic3m4n2005]

Writeback is enabled, Filetransfer is from my Raid-0 (see sig) to the Raid-5 array.
There is noc difference if it's a 700 cd image or a x GB big file, will test with small files like a MP3 folder when i get home from work.
Thanks for the chart anyway ;)