[Lustre-discuss] testing block device performance while lustre is running

[Joe Landman]

On 12/14/2010 03:33 PM, Brock Palen wrote:
> Is there a safe way to test block device read performance while
> lustre is using the device?  Example a type of read only access to
> the device to check that it is performing correctly?

Brock

   We allocate a small aligned partition before the Lustre OST partition 
for read and write testing.  If you don't have this, you might be able 
to do read testing.  The latter you would need to do with dd on the raw 
device

	dd if=/dev/sdXP of=/dev/null bs=128k count=Z

where X is the drive, P is the partition number (if any), and Z is the 
number of 128k blocks you want to read.  Don't mix up if and of 
arguments (e.g. this can be a dangerous command with a minor typo)

>
> Or is this a bad idea?

   It will impact OST performance if you wind up increasing resource 
contention.

   Regards,

Joe

>
> Brock Palen www.umich.edu/~brockp Center for Advanced Computing
> brockp at umich.edu (734)936-1985
>
>
>
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Joseph Landman, Ph.D
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