Enabling DMA

By default, some Linux installations may not enable DMA on IDE disk to ensure compatibility.

If you have a IDE drive that supports UltraDMA, you can speed up access to it considerably by simply editing a configuration file.
Note: This is ONLY for IDE drives, SCSI drives will not be affected.

Edit the file "/etc/sysconfig/harddisks" (listed below) and turn on some of the speed enhancements.
The safe options to change are USE_DMA, EIDE_32BIT and LOOKAHEAD. Changing MULTIPLE_IO or EXTRA_PARAMS can result in loss of data if you do not know what you are doing.

# These options are used to tune the hard drives -
# read the hdparm man page for more information

# Set this to 1 to enable DMA. This might cause some
# data corruption on certain chipset / hard drive
# combinations. This is used with the "-d" option
# 
USE_DMA=1

# Multiple sector I/O. a feature of most modern IDE hard drives,
# permitting the transfer of multiple sectors per I/O interrupt,
# rather than the usual one sector per interrupt. When this feature
# is enabled, it typically reduces operating system overhead for disk
# I/O by 30-50%. On many systems, it also provides increased data
# throughput of anywhere from 5% to 50%. Some drives, however (most
# notably the WD Caviar series), seem to run slower with multiple mode
# enabled. Under rare circumstances, such failures can result in
# massive filesystem corruption. USE WITH CAUTION AND BACKUP.
# This is the sector count for multiple sector I/O - the "-m" option
#
# MULTIPLE_IO=16

# (E)IDE 32-bit I/O support (to interface card)
#
EIDE_32BIT=3

# Enable drive read-lookahead
#
LOOKAHEAD=1

# Add extra parameters here if wanted
# On reasonably new hardware, you may want to try -X66, -X67 or -X68
# Other flags you might want to experiment with are -u1, -a and -m
# See the hdparm manpage (man hdparm) for details and more options.
#

EXTRA_PARAMS=

Any changes to this file will take effect after rebooting.