Dixie State College -- Computer and Information Technology

Optimizing IDE Disk I/O

Background
Most Linux distributions choose safe IDE interface configurations for default installations. This allows for successful installs, but does not always result in optimal disk performance. The notes below discuss the steps necessary to optimize your disk I/O. The information was gathered from a variety of web pages, man pages, kernel source code, and Computer Organization text books.

Disk I/O Options
Modern IDE drives have several options available to them, depending on the options available on the motherboard. The most important ones include:

Multi-block transport
Data width transport to the IDE interface.
Direct Memory Access (DMA)
Disk read ahead
OS read ahead
IRQ unmasking

Software Requirements
The following software needs to be installed.

Use the debian package hdparm.
bash# apt-get install hdparm

Special kernel support may be required for DMA. Download the latest CIT kernel build.

bash# wget /it/it3110/sources/linux-2.4.29-dsccit-y05m03d02.tgz
bash# tar zxf linux-2.4.29-dsccit-y05m03d02.tgz
bash# cd linux-2.4.29-dsccit-y05m03d02
bash# ./unpack-kern.bash

Edit /etc/lilo.conf to add the new kernel image as an option.

  image=/boot/bzImage-2.4.29-dsccit-y05m03d02
        label=y05m03d02
        read-only

Install the new configuration, and reboot to the new image.

bash# lilo
bash# lilo -R y05m03d02
bash# reboot

Kernel Driver Installation
Without the correct IDE driver, DMA will not be available.

Determine the IDE Interface chipset.
bash# grep 'IDE interface' /proc/pci
Outputs may include VIA or Intel based chipsets.
Use modconf to install the driver for your chipset. The drivers are located under kernel/drivers/ide/pci.
VIA chipsets use via82cxxx.
Intel chipsets use piix.

Drive Configuration

Test the speed of the drive.
bash# hdparm -tT /dev/hda

Determine drive capabilities.

bash# hdparm -v /dev/hda

/dev/hda:

 Model=Maxtor 6E040L0, FwRev=NAR61590, SerialNo=E1KG4BKE
 Config={ Fixed }
 RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=57
 BuffType=DualPortCache, BuffSize=2048kB, MaxMultSect=16, MultSect=16
 CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=80293248
 IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
 PIO modes: pio0 pio1 pio2 pio3 pio4 
 DMA modes: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 udma4 udma5 *udma6 
 AdvancedPM=yes: disabled (255) WriteCache=enabled
 Drive Supports : ataATA-1 ATA-2 ATA-3 ATA-4 ATA-5 ATA-6 ATA-7

Configure multi-block transport. The 16 comes from MaxMultSect above.

bash# hdparm -m 16 /dev/hda

/dev/hda:
 setting multcount to 16
 multcount    = 16 (on)

Configure for wider bus transfers. The 1 is not completely safe. There are a few older chipsets that will cause data loss. If you have one of those, then use 3. (Read the man page for hdparm).
bash# hdparm -c1 /dev/hda /dev/hda: setting 32-bit I/O support flag to 1 I/O support = 1 (32-bit)

Enable Direct Memory Access (DMA)

bash# hdparm -d1 /dev/hda

/dev/hda:
 setting using_dma to 1 (on)
 using_dma    =  1 (on)

Best DMA mode. The 70 comes from 64 + 6. 64 is because we are using UltraDMA (udma) from the output of hdparm -v. 6 is because we are using version 6 (udma6) of UltraDMA.
bash# hdparm -X70 /dev/hda /dev/hda: setting xfermode to 70 (UltraDMA mode6)

Disk read ahead

bash# hdparm -A 1 /dev/hda

/dev/hda:
 setting drive read-lookahead to 1 (on)

OS read ahead

bash# hdparm -a 8 /dev/hda

/dev/hda:
 setting fs readahead to 8
 readahead    =  8 (on)

IRQ unmasking

bash# hdparm -u 1 /dev/hda

/dev/hda:
 setting unmaskirq to 1 (on)
 unmaskirq    =  1 (on)

Test the speed of the drive.
bash# hdparm -tT /dev/hda

Make it permanent
In order to make the changes permanent accross system reboots, install a startup script to reconfigure the drive at boot time.

Create a simple shell script with the hdparm configuration command.
#!/bin/bash hdparm -u 1 -c 1 -d 1 -A 1 -a 8 -m 16 /dev/hda
Put the script in /etc/init.d/hdparm
Make a link to the script from /etc/rcS.d/S21hdparm

bash# cd /etc/rcS.d
bash# ln -s ../init.d/hdparm S21hdparm

The new kernel version needs to be made permanent. Edit /etc/lilo.conf and change the default to the new kernel.
# this is the old line. comment it out with the # #default=Linux # this is the new line. you must add it in. default=y05m03d02
Install the new lilo configuration.
bash# lilo Added Linux Added y05m03d02 * Skipping /vmlinuz.old