LVM and VxVM

Do alternate PV count for VG-PV Limit?

 
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Do alternate PV count for VG-PV Limit?

Silly question:

I have a VG with max PV of 16. The PV are LUNs. I have 2 fibre so I see each LUN four times. If I include them into a VG it looks like this:

--- Physical volumes ---
PV Name /dev/dsk/c6t0d0
PV Name /dev/dsk/c7t0d0 Alternate Link
PV Name /dev/dsk/c18t0d0 Alternate Link
PV Name /dev/dsk/c19t0d0 Alternate Link


Do the Alternate Links count as real PV for the limit in the VG? In other words, with a limit of 16PV, can I add 3 more LUN (each with 3 alternate) or 15?

Best Regards

Andreas
6 REPLIES 6
Pedro Cirne
Esteemed Contributor
Solution

Re: Do alternate PV count for VG-PV Limit?

Hi,

You may add 15 new PV to the existing VG.

Alternate links don't count for MAX PV.

Enjoy :)
Florian Heigl (new acc)
Honored Contributor

Re: Do alternate PV count for VG-PV Limit?

No, only really ' different' PVs (PVID) count in.

Good luck,
florian
yesterday I stood at the edge. Today I'm one step ahead.
Devender Khatana
Honored Contributor

Re: Do alternate PV count for VG-PV Limit?

Hi,

Alternate links are different paths to the same Physical device so do not count for the limit towards maximum PV in a volume group. You can have as many as 7 alternate links to each PV.

HTH,
Devender
Impossible itself mentions "I m possible"
generic_1
Respected Contributor

Re: Do alternate PV count for VG-PV Limit?

If you have 16 PV in your case total. This can be 16 disks or 16 luns. Luns count just the same as disks. Alternate links do not count towards PV count in either case, so no worries there. Note 16 PV in a volume group is the system default and can only be set when the VG is created. So next time you create your VG remember that you can set your PVs up to 255 :). Also consider doing striping with the -I -i options when you create your logical volumes for performace. Note to over project a bit though so you dont have to worry about extending your Volume group. The more disks in the stripe the better. Just some food for thought.
Also if you have online JFS installed
swlist | grep -i jfs # to check
you can do your PV extend online :)

GOOD luck

Re: Do alternate PV count for VG-PV Limit?

Hello,

thank you all for your help.

Jeff, I know. I didn't set up this system, I just have to ensure it will survive somehow. A re-install is (unfortunatly) no option.

Andreas

Re: Do alternate PV count for VG-PV Limit?

closed