Help File Library: Hard Drive Speed Tweak for Linux

Enabling 32-bit I/O and DMA for the hard drives

See man hdparm for complete details and cautions.

Some Linux distributions aren't optimized for your specific system, so tweaks are necessary. I run RedHat 6.1, and here is how I sped up my disk speed by enabling 32-bit I/O and DMA on my system.

The turning on/off of the 32-bit I/O and DMA has to be done by root with all root privileges. I su - and query my current settings and time the harddrive current performance:

[phil@fancypiper phil]$ su -
Password:

[root@fancypiper /root]# hdparm -c /dev/hda

/dev/hda:
I/O support = 0 (default 16-bit)


[root@fancypiper /root]# hdparm -c /dev/hdb

/dev/hdb:
I/O support = 0 (default 16-bit)

[root@fancypiper /root]# hdparm -t /dev/hda

/dev/hda:
Timing buffered disk reads: 64 MB in 17.58 seconds = 3.64 MB/sec

[root@fancypiper /root]# hdparm -t /dev/hdb

/dev/hdb:
Timing buffered disk reads: 64 MB in 17.44 seconds = 3.67 MB/sec

Both my drives are set to 16 bit and no DMA. Now, I turn on the 32 bit I/O and DMA and check the timing with the new settings.

[root@fancypiper /root]# hdparm -c 1 -d 1 /dev/hda

/dev/hda:
setting 32-bit I/O support flag to 1
setting using_dma to 1 (on)
I/O support = 1 (32-bit)
using_dma = 1 (on)
[root@fancypiper /root]# hdparm -c 1 -d 1 /dev/hdb

/dev/hdb:
setting 32-bit I/O support flag to 1
setting using_dma to 1 (on)
I/O support = 1 (32-bit)
using_dma = 1 (on)

[root@fancypiper /root]# hdparm -t /dev/hda

/dev/hda:
Timing buffered disk reads: 64 MB in 11.77 seconds = 5.44 MB/sec

[root@fancypiper /root]# hdparm -t /dev/hdb

/dev/hdb:
Timing buffered disk reads: 64 MB in 5.24 seconds =12.21 MB/sec

[root@fancypiper /root]#

Quite an improvement, especially the second drive!

You can commit these settings by commanding:

[root@fancypiper /root]# hdparm -k 1 /dev/hda

/dev/hda:
setting keep_settings to 1 (on)
keepsettings =  1 (on)
[root@fancypiper /root]# hdparm -k 1 /dev/hdb

/dev/hdb:
setting keep_settings to 1 (on)
keepsettings =  1 (on)

To apply these settings on re-boot, they must be placed in some startup file. Since I use the RedHat 6.1 distro of Linux, I add this to the bottom of my /etc/rc.d/rc.local file.

Here is my /etc/rc.d/rc.local file for an example:

#!/bin/sh
#
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.

if [ -f /etc/redhat-release ]; then
R=$(cat /etc/redhat-release)

arch=$(uname -m)
a="a"
case "_$arch" in

     _a*) a="an";;

     _i*) a="an";;
esac

NUMPROC=`egrep -c "^cpu[0-9]+" /proc/stat`
if [ "$NUMPROC" -gt "1" ]; then
SMP="$NUMPROC-processor "
if [ "$NUMPROC" = "8" -o "$NUMPROC" = "11" ]; then
a="an"
else
a="a"
fi
fi

# This will overwrite /etc/issue at every boot.  So, make any changes
you
# want to make to /etc/issue here or you will lose them when you
reboot.
echo "" > /etc/issue
echo "$R" >> /etc/issue
echo "Kernel $(uname -r) on $a $SMP$(uname -m)" >> /etc/issue

cp -f /etc/issue /etc/issue.net
echo >> /etc/issue
fi

# Added by phil
# This sets 32 bit I/O and DMA for hard drives
hdparm -c 1 -d 1 -k 1 /dev/hda

hdparm -c 1 -d 1 -k 1 /dev/hdb