i have just got a new server but i have one problem, UDMA mode will not turn on on the hard drives and is therefore killing the disk performance altogether, its RH9 with cpanel, anyone got any ideas what the problem is here
and before you ask the output of hdparm -d1 /dev/hda is
setting using_dma to 1 (on)
HDIO_SET_DMA failed: Operation not permitted
using_dma = 0 (off)
The key there is that it states you're already using UDMA2 mode.
For systems which have all of the pre-requisites for UDMA mode 3 and 4 and a hard drive capable of UDMA modes 3 and 4 a special 80 wire, 40-pin interface cable is required. The 80 wire cable reduces crosstalk and improves signal integrity by providing 40 additional ground lines between the 40-pin IDE signal and ground lines. Due to the higher transfer rate and shorter cycle times of the data transfers this cable is required to achieve UDMA mode 3 and 4 performance.
So to go up any higher... make sure it's supported by your motherboard, enabled in your BIOS, and that you're using the proper connector.
It SHOULD set itself automagicaly to the highest aviailable.
If you're daring you can use
-X68 -> ATA-66 (UDMA 4)
-X69 -> ATA-100 (UDMA 5)
hdparm -X68 /dev/hda
but this could completely cause all data to be destroyed/lost.