The DMA (Direct memory access), is computer feature that allows hardware subsystems to access system memory independent of the CPU.
There is a way to determine if a system turn on IDE DMA, you can do this by checking the proc entry cat /proc/ide/hda/settings, if using_dma is set to 1, then the DMA support is enabled.
You can do it also, by hdparm -i /dev/hda, the DMA modes line will report the possible IDE access modes the drive supports. For example:
UDMA modes: udma0 udma1 udma2 udma3 udma4 *udma5
So if you want to enable DMA you can do it by hdparm as :
hdparm -d1 /dev/hda, and this can be added to a start script like rc.local.
Or add an entry as the following to /etc/hdparam.conf in order to be automatically applied at boot.
dma = on