topic Re: PV in Operating System - HP-UX

PV

Nobody's Hero — Mon, 06 May 2002 16:52:08 GMT

Is there a limit as to how many physical volumes I can have in a volume group?
If so, what kernel parm controls this action?

Thanks,
Bob

Re: PV

Jordan Bean — Mon, 06 May 2002 16:55:08 GMT

The -p option to vgcreate dictates the maximum number of physical volumes allowed. The default is 16. The absolute max is 255.

Re: PV

Helen French — Mon, 06 May 2002 16:56:00 GMT

Hi Bob:

The maximum number of PV in a single VG - 255.

The default is 16, if you want to change this use -p option with vgcreate command.

# man vgcreate - for details.

HTH,
Shiju

Re: PV

harry d brown jr — Mon, 06 May 2002 16:57:47 GMT

do a

vgdisplay -v vg00 | more

Note the PV max - there's your limit. Yes you can change it. There is a max, of which I think it's probably around 255 with some other possible restrictions.

man vgcreate -p option

live free or die
harry

Re: PV

S.K. Chan — Mon, 06 May 2002 17:00:41 GMT

By default, the maximum logical volumes in a volume group is 255, this value can be decreased but not increased, by recreating the volume group. The maximum physical volumes per volume group is set to 16 by default, but can be decreased or increased up to 255, again, by recreating the volume group. See "-l" option in vgcreate.

Re: PV

S.K. Chan — Mon, 06 May 2002 17:01:45 GMT

Sorry .. I meant "-p" option. No kernel parameter is involved here.

Re: PV

Victor_5 — Mon, 06 May 2002 17:15:52 GMT

The max is 255, man vgcreate and see the "-p" switch.

Re: PV

Wodisch — Mon, 06 May 2002 17:25:59 GMT

Hi Robert,

there a two limits:
- an absolute one: 255 PV / VG
- an relative one: the amount of PVs configured when the VG was created (default: 16)

So, whatever is lower will be your limit, and since you cannot modify these parameters later on, you'll have to do it right from the very beginning!

Oh, and there is no kernel parameter for PVs / VG, there is only one about the amount of VGs / computer ("maxvgs").

HTH,
Wodisch

Re: PV

James R. Ferguson — Mon, 06 May 2002 17:33:30 GMT

Hi Robert:

As already noted, the maximum number of physical volumes in one volume group is 255 (ranging from 1-255) with a default of 16 during 'vgcreate'. Too, once set, it cannot be changed for the volume group unless you destroy and recreate the group. No kernel parameter is directly involved or tunable.

I think, however, that you may be thinking of another of the kernel parameter 'maxvgs'. This is tunable and controls the maximum number of LVM *Volume Groups* that can be created and/or activated on the system. The default is 10 and the allowable range is 1-256.

Regards!

...JRF...

Re: PV

Rita C Workman — Mon, 06 May 2002 17:37:37 GMT

Hi Robert,

Everyone else has explained completely what the max # of pv you can have in a vg.

As was said there is no kernel parm that controls this BUT ...I have found some folks believe maxvgs has something to do with # of pv in a vg. Just to augment another bit of info on this for you....

maxvgs is how many vg you can create on a system.
If your maxvgs is set to 10 than you can create vg with the minor number of 0-9. So minor numbers such as 0x0a0000 or 0x10000 would be unable to create.
Hex converted to dec
0a = 10
0b = 11
10 = 16
11 = 17

To allow for additional creation of vg's you would have to increase the parm maxvgs & reboot.

Like I said, just adding a tidbit here..hope you don't mind.

Rgrds,
Rita