One of the IDE hard drives in a server is transferring data very slowly. What command must be run
to enable DMA on it?

A.
hdparm -d /dev/hda

B.
hdparm –dma /dev/hda

C.
hdparm –dma /dev/hda1

D.
hdparm -d /dev/hda1

E.
hdparm -d1 /dev/hda

Explanation:
hdparm provides a command line interface to various kernel interfaces supported by the Linux
SATA/PATA/ SAS “libata” subsystem and the older IDE river subsystem. Many newer (2008 and later)
USB drive enclosures now also support “SAT” (SCSI-ATA Command Translation) and therefore may
also work with hdparm. Eg. recent WD “Passport” models and recent NexStar-3 enclosures. Some
options may work correctly only with the latest kernels.
-d Disable/enable the “using_dma” flag for this drive. This option now works with most combinations
of drives and PCI interfaces which support DMA and which are known to the kernel IDE driver. It is
also a good idea to use the appropriate -X option in combination with -d1 to ensure that the drive
itself is programmed for the correct DMA mode, although most BIOSs should do this for you at boot
time. Using DMA nearly always gives the best performance, with fast I/O throughput and low CPU
usage.