extending VG problems 1

[Mag0007]

Trying to extend a vg getting this error

# extendvg uservg hdisk115

0516-1162 extendvg: Warning, The Physical Partition Size of 16 requires the creation of 6535 partitions for hdisk115. The limitation for volume group uservg is 3048 physical partitions per physical volume. Use chvg command with -t option to attempt to change the maximum Physical Partitions per

Physical volume for this volume group.
0516-792 extendvg: Unable to extend volume group.

This is very import VG, so would the chvg command do anything to solve this?

 

[usige]

Mag0007,
chvg -t could help you in this case. Right now the uservg is set to a factor of 3 but you would need at least a factor of 6 for based on the error message (1016*6 = 6096 pp's per pv). You can change the factor with the following command:

chvg -t 6 uservg

On thing to keep in mind is that increasing the factor reduces the number of physical volumes the vg can support. Assuming a standard vg with a factor of 6 you can only support 5 pv's in the vg (32 / 6 = 5.333). If the vg is a "big vg" it would be 21 (128 / 6 = 21.333). You can convert to a "big vg" with the command:

chvg -B uservg

Hope that helps.

 

[usige]

Oops, I re-read the error message and the factor would need to be atleast 7 not 6. This means only 4 pv's or 18 for big vg's.

 

[p5wizard]

Or get two or more smaller disks (SAN volumes?) to extend the VG - something slightly less than half the size it is now. Your hdisk116 is 104.5GB and the max disksize for this VG (factor 3) is 48.7GB. For roughly the same size expansion, 3 volumes of 35GB should do the trick...


HTH,

p5wizard

 

[usige]

p5wizard makes a good point. If this is a san disk you are better off presenting smaller luns. Changing the factor means you effectively end up "wasting" available pp's on the smaller disks (i.e. you reserve 7112 pp's per disk but smaller disks might only use 2048 pp's of their reserved space).

 

[Mag0007]

p5wizard:How did you know my SAN lun was 104.5GB? I have trying to find that out myself.

lspv hdisk116 just shows thats no VG is assign to it.

Also what would happen if I try to force this PV into my VG?

 

[p5wizard]

Math...

It's gotta be between 6535 and 6356 times 16MB

0516-1162 extendvg: Warning, The Physical Partition Size of 16 requires the creation of 6535 partitions for hdisk115.

HTH,

p5wizard

 

[Mag0007]

aa yes. But is it possible to find out without using this command?

 

[p5wizard]

bootinfo -s hdisk115

That's what AIX OS install script uses to determine disk size and then decides how to create rootvg (PP size) when doing a new/overwrite install. Hence the name of the command.

HTH,

p5wizard

 

[Mag0007]

p5wizard and usige:

"Changing the factor means you effectively end up "wasting" available pp's on the smaller disks"

My situtation is this: uservg is on SSA, and I am trying to move this off SSA to SAN.

So I am trying to introduce the SAN disk into uservg, so I can move the LVs over....

Can you guys think of a better way?

 

[p5wizard]

If you intend to move everything off SSA, then you can go with chvg -t 7, if there are 3 disks or less in the VG at this time, then migratepv all the data to the SAN volume.

If there are more than 3 disks already in the VG, then you can't add this big SAN volume to the VG. Unless it is a BIG VG as usige pointed out.


HTH,

p5wizard

 

[Mag0007]

lsvg -p vg shows
8 disks (all SSA)
Same of these disks are 34 gigs, and some are 9 gig

lsvg vg shows
16M ppsize
Total:15746 PPs

My san disks are:104G x 4 disks

So I do have enough SAN space.

So, you think I should get smaller LUN size allocated, like 30 gigs and just extendvg into vg?

 

[p5wizard]

Your -t factor is now 3, that means you can have up to 10 PVs of 3048 PPs in the VG, so you have room for 2 extra disks in the VG. (or 34 if it is a big VG)

Your best bet is to get SAN volumes of roughly the same size as the SSA disks and migrate them one at a time. Then after you have emptied (migratepv) one of the SSA disks, you can reducevg the SSA disk and extendvg another SAN volume. keep on doing this until all SSA disks have been migrated to their SAN volume counterpart.

If BIG VG, you can chvg -t 7 and add the big SAN volumes and migrate to those disks. If your VG is not BIG VG, you can convert it to BIG VG, but I think it needs free space on every disk (not sure of this though).

All this is guesswork, so please post the output of "lsvg uservg" and "lsvg -p uservg" and I'll have another look.


HTH,

p5wizard

 

[Mag0007]

VOLUME GROUP: uservg VG IDENTIFIER: 00046251f5fb1953
VG STATE: active PP SIZE: 16 megabyte(s)
VG PERMISSION: read/write TOTAL PPs: 15746 (251936 megabytes)
MAX LVs: 256 FREE PPs: 4748 (75968 megabytes)
LVs: 6 USED PPs: 10998 (175968 megabytes)
OPEN LVs: 5 QUORUM: 1
TOTAL PVs: 8 VG DESCRIPTORS: 8
STALE PVs: 0 STALE PPs: 0
ACTIVE PVs: 8 AUTO ON: yes
MAX PPs per PV: 3048 MAX PVs: 10

$ lspv -p uservg

PV_NAME PV STATE TOTAL PPs FREE PPs FREE DISTRIBUTION
hdisk40 active 2172 93 00..00..00..00..93
hdisk5 active 2172 130 00..00..00..00..130
hdisk10 active 2172 1376 435..00..72..434..435
hdisk15 active 2172 2093 435..355..434..434..435
hdisk37 active 542 17 00..00..00..00..17
hdisk28 active 2172 0 00..00..00..00..00
hdisk13 active 2172 232 00..00..00..00..232
hdisk14 active 2172 807 00..00..00..372..435

 

[p5wizard]

If you can get smaller size SAN LUNs (say 5 LUNs of 40GB), they can fit in your existing VG (2 of them initially), then as you migratepv the SSA disks to empty them, you can free up PV slots in the uservg and fit the remaining 3 SAN LUNs.

Example:

If these are your new 40GB LUNs
hdisk201
hdisk202
hdisk203
hdisk204
hdisk205

then

extendvg uservg hdisk201
extendvg uservg hdisk202
migratepv hdisk40 hdisk201
migratepv hdisk5 hdisk202
migratepv hdisk15 hdisk202
reducevg uservg hdisk40
reducevg uservg hdisk5
reducevg uservg hdisk15
extendvg uservg hdisk203
extendvg uservg hdisk204
extendvg uservg hdisk205
migratepv hdisk10 hdisk203
...

You get the idea. For the last SSA hdisks, you might have to specify more than one destination PV - just a bit of math...

Also you might want to use a different order to group the LVs each in one PV? That's up to you.

syntax: migratepv [ -l LVname ] fromPV toPV1 [ toPV2 ... ]

migrate PPs [ only those belonging to LVname ] from fromPV to toPV1 [ and toPV2 and ... ]

see also the man page...


HTH,

p5wizard

 

[Mag0007]

p5wizard:

THANKS! Good post!

Can I use my 104GB lun now? Assigning space here will take almost 3 months.... :-(

Star deserved!

 

[p5wizard]

Well, no because it is too big to fit in the uservg as is and you can't increase the -t parameter anymore because there are already 8 PVs in the uservg.

If you can accommodate some downtime, then I guess you could create a new VG with a bigger PP size on the big LUN and create new LVs/FSs and copy over the data.

Your other option is to convert the VG to BIGVG - see man page for chvg. Option is -B


HTH,

p5wizard

 

[Mag0007]

p5wizard:

Thanks for the clean and simple explanation..!