Max PE per PV

[Bruno Bossier_1]

I remember in the past that there was a problem when you add a disk to a previously created volumegroup that the "Max PE per PV" is defined by the first disk of the volumegroup. So, when the new disk that is added is bigger than the first disk that you can't use the full capacity of this new disk.

Is that still the case ?

Bruno

[Pete Randall]

Yes, it is. The max pe and pe size can only be defined at vgcreate time, and, if left to default, will be adequate for only the original size disk.


Pete

[Bruno Bossier_1]

OK, thanks !

Bruno

[Steven E. Protter]

It can be the case.

There are a few ways to avoid the problem.

When creating the volume group use the -p parameter

-p 10 means there will not be more than 10 physical volumes in the volume group. That gives you more PE's to use on actual physical volumes since the normal setup tries to spread the available PE's over the maximum number of physical volumes, which is 255.

You have the option of using larger size for each PE as well.

-s

-e

Can be useful.

Picking a -p number thats reasonable and allows for growth however is the most useful approach in my opinion.

Note that all of this has to be done when the volume group is created. If you run into a problem you have to back up and rebuild the volume group.

SEP

[Bruno Bossier_1]

Problem is that the volumegroup already exists :-(

Thanks anyway !

[Bill Hassell]

This is one of those plan ahead situations. You can create a VG with a dozen disks using a single vgcreate. Just put all the physical disks on the same line and the VG will be created slightly larger than necessary. vgcreate uses the information you provide to create the extent table but this is not dynamic--once the extent table is created, that is the absolute largest that the VG can be.

So in the future, always use the -s and -e options to make sure there is plenty of room for expansion. Having lots of extra extent entries does not have any performance penalties so always make potentially growing VGs extra large.