Volume Group was given a 100gb lun but could only use 50gb of it

[Mark Parsons]

Hi All,

I've got an HPUX 11.11 server which has a volume group of 200gb made up of 50gb x 4 luns. I've now added a 100gb lun to it but when allocated to the volume group only 50gb of it was added (a warning message did flash up but I missed it). So the volume group should be 300gb but is only 250gb and 50gb has been left in limbo.

What fixes this if anything - is it physical extents or is there a maximum lun size of 50gb on HP11.11?

Kind Regards,

Mark P.

[donna hofmeister]

a vgdisplay would be helpful...

there might be something in syslog that is relevant to this situation...

[Pete Randall · Accepted solution]

The max_pe and pe_size were set when the VG was created, apparently to accomodate your 50GB LUNs.  You could remove the 100 GB LUN and re-allocate it as 2 50 GB LUNs or you could alter the VG definitions.  If you were using 11.31, this could be done with vgmodify.  Earlier releases require re-creation of the VG.

[kgpenator]

Hi Pete,
Could you post how to alter VG definitions? I also faced the same issue

[Bill Hassell]

For 11.23 and 11.31, use the command vgmodify. You must increase the maximum PE (physical extents) for LUNs (PVs or physical volumes). For 11.11, there is no supported way to do this except to backup all the data and rebuild the VG from the beginning. If you have an HP support engineer you can call, they may be able to get you a copy. There is no vgmodify for 11.00 or earlier.

This brings an important lesson for creating volume groups. Do not use the defaults if the VG will grow. When you are dealing with GB size VGs, always increase the PE size to 16 or 32, 64 for TB sized VGs. And calculate the max PEs per PV for the largest disk you'll ever add to the VG. If you don't know, then specify a large value such as 40,000 or more. This simply reserves space in the LVM headers to present larger disks. It will save you from having to rebuild a VG all over again.