topic Re: pysical extent sizes on 36GB disk in Operating System - HP-UX

pysical extent sizes on 36GB disk

Gerald Taylor — Thu, 10 May 2001 18:36:21 GMT

I am running hpux 11.00 I would like to know what is the best way to configure the pysical extent sizes of 36GB disk in SC10 enclosure. The system will be running Oracle 8. I would also like to know if there is any documentation on how to set PE and block size depending on how large your disk are? Thanks for any help.

GGT

Re: pysical extent sizes on 36GB disk

A. Clay Stephenson — Thu, 10 May 2001 18:49:47 GMT

Hi Gerald,
I would think that pe size has essentially no impact on performance since the pe size is so much bigger than block size. I am assuming that you have enough pe's to handle the largest device in your volume group. A more important parameter in the logical volume stripe size. Every reference I have seen indicates that 64K is optimum. I assume that you are using VxFS. I would also suggest that you use the vxfs mount options convosync=direct and mincache=direct so that the buffering is done in the SGA and not also in the UNIX buffers. This gives you all the benefits of raw disks and none of the drawbacks.

My 2 cents, Clay.

Re: pysical extent sizes on 36GB disk

James R. Ferguson — Thu, 10 May 2001 18:55:34 GMT

Hi Gerald:

There is a very good Knowledge Base document (#KBRC00004285) titled "Effects of setting large max_pe values for volume groups" which should answer your second question.

...JRF...

Re: pysical extent sizes on 36GB disk

MANOJ SRIVASTAVA — Thu, 10 May 2001 19:02:14 GMT

Hi Gerald

The PE size also should be similar to the block size oracle uses generally 4 MB too so create using that value and it will give you a better performance .

Manoj Srivastava