Linux Hard Drive Performance measurements

Many people trust vendor specs, moreover they trust hard drive speed, disk controller speed and so on. However, reality is that you will never get those specs when you set up the hardware. Why? Vendors test their hardware on special environments, with specific combination of hardware.

I was trying to set up a server with fast access to hard drives so I did a little research of how to test different configuration of hard drives. These are my findings:

Note: All these tests should be executed several times. The real results are affected by hard drive cache, controller cache, and operative system cache.

1- (Read Speed) hdparm -t /dev/sda

This is a very well known command that It can give you the max read speed (sequential).

2- (Write Speed) dd count=1k bs=10M if=/dev/zero of=/data/test.img

This is another well known command that It can give you an average of writes.

This command creates a 10G file and measure the speed.

3- (Write speed) This people http://www.nlanr.net/Dskwtst/ created a C program that logs write speed.

#wget http://www.nlanr.net/Dskwtst/Software/dskwtst.c

#gcc -O2 dskwtst.c -o dskwtst

(Compiling probably you would get an error)

dskwtst.c: In function âmainâ:

dskwtst.c:32: warning: incompatible implicit declaration of built-in function âexitâ

This error is only a warning so it should not affect results.

#./dskwtst > /data/ouputfile 2> ./log

The command will create a file on /data/ and it will send the results to log.

4- (Random access)This guy http://www.linuxinsight.com/how_fast_is_your_disk.html created a C program that can measure the seek time of the hard drive.

#wget http://www.linuxinsight.com/files/seeker.c

#gcc -O2 seeker.c -o seeker

#./seeker /dev/sda

Enjoy it ...