What is PVG

[Tommy Yip]

I'm the new user of HPUX, can anyone tell me what is PVG, and what is the different between doing mirror with separate disk and mirror with other PVG.

[Printaporn_1]

Hi,

it is for seperate disks in vg to groups for mirroring benefit , that you can control the LV allocation of PE to the right disks.

[S.K. Chan · Accepted solution]

In my own way I call it a "dirty" mirror (no PVG) vs a "clean" mirror (with PVG). Imagine you got 4 disks (A,B,C,D) and you're going to setup you VG.
Clean-mirror
============
You would setup the VG by putting A and B in PVG1 & C and D in PVG2 when you create your VG the first time using "-g" option to define the PVG name. Now when you create you LVs and you want to mirror say 1 copy you would want the mirrored copy to reside in a separate PVG instead so that you know your mirrored copies are always in PVG2 for example. This would also help in disaster recovery situation. The "lvcreate" command has "-s g" option that tells it to do a PVG-strict mirror. Going forward extending your existing LVs would just be a straight forward "lvextend" since it was already defined as PVG-strict.
Dirty-mirror
============
You setup the VG in a normal manner. In the creation of your LVs, if you simply say mirror 1 copy and let LVM figure out where to put it's mirrored copy then you may end up in a siuation whereby your mirrored copy can reside anywhere in A,B,C,D even on the disk where the primary copy sits ! Having said that you can actually tell lvextend to put your mirror-copy to a specific disk but then you would have to keep track of the PEs, etc, etc. If PVG is setup this is done automatically.

[Tom Geudens]

Hi,
There was a fine discussion about this not so long ago ... where was it again ... ah, found it : http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x437142308663d611abdb0090277a778c,00.html

For more information, just search the forums with keyword 'PVG'.

Hope this helps,
Tom

[kish_1]

Hello,
Go through the document B3936-90065.pdf in docs.hp.com
you will have good knowledge of PVG,LVM and mirroring

[steven Burgess_2]

Hi

Have a look at the attached also

Regards

Steve

[Victor_5]

Take a look this paper, you also can get it from IRTC, no is KBAN00000091. Enjoy!