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Enable DMA on disk - against slow disk speed

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We had a server performing pretty poorly and we went to investigate.
It seemed the disk speed was ~ 2.15 MB / sec, which isn't good.

First check if DMA is enabled on the disk with following command:

# hdparm -d /dev/hda

You should get the following output:

/dev/hda:

using_dma    =  0 (off)


Now let's enable DMA for the disk:

# hdparm -d 1 /dev/hda


You will see that DMA is enabled now and the disk speeds are much faster!

Remark: this has been tested with older ATA disks and is no longer relevant for newer harddisks.