[OpenAFS] Vice Partition Effects on Disk I/O

Sam Hartman hartmans@mekinok.com
09 Sep 2001 17:01:55 -0400

Does this server have fewer partitions than servers with smaller
disks?  Do you see the performance problems when the server is under
load or even when the server is just configured?

There are some cases wher youp can get better performance with many
SCSI LUNs than you can with fewer SCSI LUNs.  I'd be surprised if it
was enough to be a major factor.  Basically what happens is that you
can have number of LUNs times tagged command queue depth outstanding
SCSI ops at a time.  IF this isn't enough then you might run into
problems where SCSI operations take longer and you wait in IO wait
more for each operation.

If you have significantly more volumes on a partition and have lonts
of volumes, you may be running into problems with the volume headers
in the root directory of the volume.

I'd look at trying to determine what factors matter in the performance
problems.  IS it the partition size?  Is it the data per partition?
Is it the volumes per partition?