topic Phisical extend in Operating System - HP-UX

Phisical extend

Marcelo_33 — Thu, 16 Dec 2004 17:11:12 GMT

Bueno mi consulta es referente a los physical extend se que se generan cuando creo los logical volumen pero mi duda es saber para que sirven o cuale s su funcion apaarte si lso creo de mayor tamaño que 4mb enq ue me benefici

Re: Phisical extend

Patrick Wallek — Thu, 16 Dec 2004 17:41:42 GMT

I'm not sure exactly what you are asking, and the translation tool I found didn't do a very good job.

I *think* you are asking about 4MB being the default physical extent size when creating a VG. That is correct. I would recommend that you create the PE size larger if you have disks that are fairly large, like 36GB or greater. I create most systems with 8MB PE sizes for VG00 disks of 18 or 36GB. For larger disks I would probably go up to 16 or 32 MB PE sizes depending on the disk size and the VG.

Be aware that once a VG is created, there is not really any supported way of increasing the PE size without backing up the data, recreateing the VG, and then restoring the data.

I hope this answers your question.

Re: Phisical extend

Deoncia Grayson_1 — Thu, 16 Dec 2004 19:13:11 GMT

Physical extent question translated in English:

Well, my question is about Physical Extends (PE), I know that the PE are configured when I create the LV...., but my question is How Can I know what is the PE function and what does affect when I set up to more than 4 MBytes...?

Re: Phisical extend

Sridhar Bhaskarla — Thu, 16 Dec 2004 21:48:53 GMT

Hi,

PEs are created when you add the PV to the VG. When you create an LV, a logical to physical extent mapping is done.

PE size doesn't impact the performance unless you have configured extent based mirroring. In that case the stripe size is equal to the extent size.

The VGRA is written on each PV in the first extent. Depending on the number of PVs, LVols etc., the default 4 MB PE may not be sufficient to hold the VGRA. So, you will need to increase the PE size in that case or adjust other parameters.

-Sri