topic Re: Disk Capacity Limit in Operating System - HP-UX

Disk Capacity Limit

Piotr Kirklewski — Tue, 20 Feb 2007 14:22:26 GMT

Hi there

I'm mirroring disks, and there is an error regarding disc capacity limit for vg03.
How to change the Disk Capacity Limit for volume group ?

Cheers

Re: Disk Capacity Limit

Sandman! — Tue, 20 Feb 2007 14:24:18 GMT

Please post the exact error message you are getting.

~thanks

Re: Disk Capacity Limit

A. Clay Stephenson — Tue, 20 Feb 2007 14:36:05 GMT

When a volume group is created there are severval values that are set and remain fixed thereafter. For example: max_pv's and maxPe's. Moreover, while you may have enough free extents in a volume group to allow a mirror, you may not have enough free pe's on separate PV's to conform to the allocation policy. Please post your exact error message.

Re: Disk Capacity Limit

Piotr Kirklewski — Tue, 20 Feb 2007 14:37:25 GMT

The error is:

At least one of the disks you have chousen is larger then the maximum size allowed by volume group vg03 (8676 Mbytes). These disks can still be used, but any capacity beyond the volume group limit will be wasted.

Re: Disk Capacity Limit

hpuxrox — Tue, 20 Feb 2007 14:40:21 GMT

Clay is correct. However, hitting the MAX_PV limit is the most common. The architect should always allow more that the default value within LVM. I usually go 64, although always take in to consideration the needs and future needs of the system.

Re: Disk Capacity Limit

A. Clay Stephenson — Tue, 20 Feb 2007 14:42:03 GMT

It means exactly what it says. The max_pe value was set when the VG was created and can't be increased. When you create a VG, it's wise to anticipate the largest disk (or LUN) that you will ever wish to use and set the max_pe's and pe_seize accordingly. You have two choice. 1) Backup, Build the VG from scratch, Restore 2) Use the larger disk but be prepared to have a portion of it unaccessible. 3) Rather than adding 1 large disk add two smaller disks to the VG (OK that's 3 but who's counting?).

Re: Disk Capacity Limit

hpuxrox — Tue, 20 Feb 2007 14:42:44 GMT

You posted before i could refresh, looks like you have reached MAX_PE.

Re: Disk Capacity Limit

James R. Ferguson — Tue, 20 Feb 2007 14:48:28 GMT

Hi Peter:

> At least one of the disks you have chousen is larger then the maximum size allowed by volume group vg03 (8676 Mbytes). These disks can still be used, but any capacity beyond the volume group limit will be wasted.

This reflects that the LVM geometry is fixed at the time of volume group creation ('vgcrete'). That is, elements describing the geometry like 'max_pe' and 'pe_size' are fixed and cannot be changed.

Large physical disks may require larger values to be fully utilized. To circumvent this problem, backup your data; destroy the volume group ('vgexport', or 'vgremove'); and create it again ('vgcreate') specifying appropriate values for 'max_pe', 'pe_size' and perhaps 'max_pv' and 'max_lv'. See the manpages for 'vgcreate' for more information.

Regards!

...JRF...

Re: Disk Capacity Limit

James George_1 — Tue, 20 Feb 2007 14:53:15 GMT

Hi

As everybody has replied, this is the max_pe extends problem . Make it a practice to add the largest disk when u create the Volume groups.

Rgds / James

Re: Disk Capacity Limit

hpuxrox — Tue, 20 Feb 2007 15:01:17 GMT

Also, keep in mind that there is 64k PE limit per volume group. So, with the default PE_SIZE 4M, you will have a 256M limit on the file system. I would recommend a PE size of atleast 16M and MAX PV of 64 for any SAN attached storage. There is very little performance impact for doing this.

Re: Disk Capacity Limit

Geoff Wild — Tue, 20 Feb 2007 15:28:48 GMT

Or set the limit at the start with vgcreate:

Example:

vgcreate -s 32 -p 64 -e 32768 /dev/vg35 /dev/dsk/c11t1d4 /dev/dsk/c13t1d4 /dev/dsk/c15t1d4

That allows me to add a LUN up to 1TB in size (well 1048576 MB)

man vgcreate for more info

Rgds...Geoff