How to extend a PV.

[Jesper Sivertsen]

If i have a PV on a san-system, is it possible to extend the PV in LVM if i extend the stripeset on the san-system.

[Patrick Wallek · Accepted solution]

No, that is not possible with HP-UX and LVM.

Your best bet is to just create a new LUN on the array, present it to your system and then extend the VG and the LV and filesystem.

[TwoProc]

Patrick's right - if you want *that* pv bigger and this is the requirement - you'd have to take it out and put it back in again (can bring up a raft of issues and limitations). And you don't want to do that when you can just add a lun with the new space and add it to your vg.

[John Jimenez]

I have had issue with this problem for a couple of years. I have been backing up LUN's Creating a new larger LUN and restoring data.
What effect will having multiple LUNS have on the O.S.? I would think that there would not be any negative issues. But on the other hand won't the AutoRaid of the SAN run less efficient or better efficient or is it smart enough to deal with it?

[TwoProc]

Actually, you can conceptually get a small boost in performance per pv you add. It increases the SCSI "width" in a sort of depth sense for a file system. In other words, if you presented a file system as one, big, LUN then you're going to look like you're handling this with on scsi depth queue. If you add more pv's then you've got more of them to handle responses to the file system with - but not in a depth sense - but in a width sense - like parallel (depending). Of course, there are commands to increase the depth of a single scsi queue (which I can't think of right off). Keep in mind that even I said SCSI that really extends to most any pv type including fiber (which uses a piece of the SCSI layer).