Fair enough. I could perhaps have done a better job in explaining what i mean:

You cannot convert a classic or a big VG into a scalable VG. At least not in a sensible way, because you cannot change the PP size of a VG and you cannot change the disk layout. Therefore you need (or, if you like that wording better: i strongly suggest) to do a backup of the old VG, recreate it anew and then restore it.

The thing is: you have right now 29 disks (a "LUN" *is* a disk, albeit a virtual one) or, rather, PVs in your VG. (I use the terms "disk", "LUN" and "PV" synonymously here as a "LUN" from the storage POV is a "disk" or, rather, a "hard disk device" from the OS POV and a PV from the LVMs POV.) The maximum number of PVs is 32 and although this has changed in scalable VGs you still want to have a manageable number of disks in your system. I have administrated systems with 1500 hdisks and it is a nightmare - avoid that at all costs. When you recreate the VG it therefore makes sense to create - instead of 29 LUNs having a total of 5.2TB - the smallest possible number of LUNs with the same total amount of storage and build the new VG there. Depending on your LVs being mirrored or not, your LUNs coming from a single storage box or several (this is sometimes done for load balancing reasons), etc., etc., you want to have 3-4 (or maybe two or even one) LUN for the whole new VG in the end.

Most storage systems offer the possibility to increase LUNs in size. If your system does you can use chvg -g to make the VG aware of such an increased LUN instead of adding new LUNs to the VG to accomodate increased storage demands over time. I suppose the 29 disks you have right now have grown over time by adding one or two disks at a time. You should stop that in the future and instead increase the size of the LUNs so you won't hit the 32-disk-barrier in the future.

Really? To quote yourself:

When you recreate the VG Note that there is a parameter "Max PPs per PV" (or similar, i have no AIX system at hand to look at) which you can set. Note that this is done in steps of 1024, so the value you set there is multiplied by 1024 to give the actual maximum. The maximum number you can enter is IIRC 2048 giving you 1024x2048 ~ 2 million PPs per PV.

I hope this helps.

bakunin