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tramni1980 08-07-2009 09:53 AM

lvm: PE size, number of stripes and stripe size considerations
 
Hello!
I intend to set up my future Slackware-13.0 installation with LVM. I have already read the available How-To, but there are are still three parameters that I feel uncertain how to set. These are the size of the physical extents (PE), the number of stripes and the stripe size. The documents I have come upon so far only seem to tell how to set these parameters to certain values, but not WHY these particular values are selected. Are there any rules/reasons to follow with regard to the choice of the these parameters?

Thank you very much for your attention.

Regards,
Martin

MensaWater 08-07-2009 11:19 AM

For most uses the defaults are all you need.

The reason you might want to select something other than defaults is usually for Database products like Oracle. To optimize reads/writes sometimes it would be recommended you use a certain block size. You could help insure the disks are optimized by limiting PE size. Often your main concern in a database is IOPS (I/O per second). This can be maximized by insuring the stripe size is close to the normal block write of the DB and you insure that stripe is spread across as many disk spindles as possible (number of stripes). Usually when this is important you'll end up with unused space because to get the performance you want you usually buy your disks based on IOPS rather than capacity.


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