Interesting Tech Note for Linux – Testing the read speed of a hard disk


I look at IBM’s support feeds every day to see what interesting new info comes down the fire hose … this was a first one: Linux drive performance testing! I work with allot of Linux and AIX so this is interesting stuff, I just did not think I would see it in an IBM support feed.

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Problem
How can I test to see if all drives are reading at the same speed?
Cause
One reason that hard disks fall out of RAID arrays is a difference in read/write speeds between the drives in the RAID array. You can use the hdparm utility to test each disk to determine whether all disks are reading at the same speed.
Resolving the problem
To run the tests follow the steps below:
Telnet into the server and log in as an administrative user.
Get a list of all hard disks on the system:

wd disk-info

Run the following command on each hard disk on the system:

hdparm -Tt /dev/Disk

Example: hdparm -Tt /dev/sda

The output will look similar to the following:

/dev/sda:
Timing cached reads: 14036 MB in 2.00 seconds = 7027.55 MB/sec
Timing buffered disk reads: 226 MB in 3.02 seconds = 74.79 MB/sec

For hard disks to work together in a RAID, the read speeds should be similar to each other. For best results you should run this test multiple times on each disk and average the results.

Problem
How can I test to see if all drives are reading at the same speed?
Cause
One reason that hard disks fall out of RAID arrays is a difference in read/write speeds between the drives in the RAID array. You can use the hdparm utility to test each disk to determine whether all disks are reading at the same speed.
Resolving the problem
To run the tests follow the steps below:
Telnet into the server and log in as an administrative user.
Get a list of all hard disks on the system:

wd disk-info

Run the following command on each hard disk on the system:

hdparm -Tt /dev/Disk

Example: hdparm -Tt /dev/sda

The output will look similar to the following:

/dev/sda:
Timing cached reads: 14036 MB in 2.00 seconds = 7027.55 MB/sec
Timing buffered disk reads: 226 MB in 3.02 seconds = 74.79 MB/sec

For hard disks to work together in a RAID, the read speeds should be similar to each other. For best results you should run this test multiple times on each disk and average the results.

 

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