DMA RAID query

[dave s]

Hi all,

I have a working RAID 1 setup

hda HDD 180GB RAID
hdb DVD burner/reader
hdc HDD 180GB RAID
hdd DVD reader

hdparm -tT /dev/hda and hdc gives ...

1278MB/sec cashed reads
62MB/sec bufferd disk reads

Which seems respectable for new 7200 Hitachi drives. (I did not setup DMA, my 
BIOS did it for me) I was warned never to mix a HDD & a CD/DVD burner as it 
degrades the HDD speed.

I removed hdb and hdd, rebooted and did another hdparm -tT and got the same 
results.

I was going to install a PCI ATA controller for the two DVD drives but am 
unsure now if it is worth it, can anyone comment (1st time RAID user :)

Dave