topic Re: How to extend pv? in Operating System - Linux

How to extend pv?

Andrej Vavro — Fri, 15 Apr 2005 09:34:29 GMT

Hi guys,

I've created physical volume by pvcreate in time when I had 6 disks in HW RAID. Total amount was about 135GB. Later I've added 4 more disks and pvdisplay can see only original 135GB. Is there any way how to extend pv? I mean instead of backup, pvcreate, vgcreate, lvcreate and restore.

Is on SLES7 and IBM EXP300 storage expansion unit.

Any advice is appreciated.

regards,
Andrej

Re: How to extend pv?

Rick Garland — Fri, 15 Apr 2005 11:52:23 GMT

Does the system see the disks? Is the RAID configuration accounting for these additional disks?

There is not a command to pvextend. You can pvcreate to tell the OS that these disks are part of LVM config. You can do vgextend to put these disks in the same volume group.

The pvcreate command is destructive so make sure you are working with the correct disks.

Re: How to extend pv?

Stuart Browne — Fri, 15 Apr 2005 18:44:35 GMT

Go Rick! Go Rick! *cheers!* The perfect answer!

*mumbles 'cause Rick got there first*

Re: How to extend pv?

Steven E. Protter — Mon, 18 Apr 2005 01:15:01 GMT

Usually you do this:

vgextend
lvextend < if you need to extend an existing volume group>
extendfs < to extend the current filesystem >

pvcreate is not going to hurt any new disks.

The reason you probably don't recognize the size thats available is because the vgcreate command did not accomodate the current configuration.

To fix that, you have to vgexport the current volume group and re-run the vgcreate command. If in that command you limit the number of physical volumes to significantly less than 255, the maximum, more space will be able to be allocated on existing volume groups.

I can provide specific commands on Monday when I regain access to an HP-UX server.

SEP

Re: How to extend pv?

Andrej Vavro — Mon, 18 Apr 2005 01:47:58 GMT

Steven,

Can you please provide more details on suggested solution? Are the existing data going to be lost?

Thanks,
Andrej

Re: How to extend pv?

Stuart Browne — Mon, 18 Apr 2005 02:49:40 GMT

Assuming you don't remove the existing physical volumes (pv's) from the current volume groups (vg's), no existing data should be lost.

If you are at all unsure about what you are doing, standard rule of thumb. Back it up first!

With the 4 disks you added to the RAID container, has the existing RAID container been expanded?

If so, have you created new partitions on the existing container? Or has the new disks been added as a new container?

You create PV's under Linux on filesystems that have been created, or whole physical (or RAID logical) device.

So first step I guess.. What did you actually do with those new 4 disks?

Once you've created a PV with the new space, then you 'vgextend'.

'vgdisplay' will show:

--- Volume group ---
VG Name vgLocal
VG Access read/write
VG Status available/resizable
VG # 0
MAX LV 256
Cur LV 3
Open LV 3
MAX LV Size 255.99 GB
Max PV 256
Cur PV 1
Act PV 1
VG Size 107.88 GB
PE Size 4 MB
Total PE 27617
Alloc PE / Size 27617 / 107.88 GB
Free PE / Size 0 / 0
VG UUID 0sUVMR-PuRI-5Hd0-30m5-jeFl-LX2Q-6JnGGs

The 'PE' values (Physical Extents, which live on Physical Volumes) are how much of the PV's have not yet been assigned to a volume group.

.. I love LVM .. don't you ? :)

NOTES: As listed above, depending on what values for PE size the volume group is created with, depends on how big it can go. 4MB PE's can grow up to 256GB LV's.

Re: How to extend pv?

Andrej Vavro — Tue, 19 Apr 2005 01:55:14 GMT

Guys,

sorry for bothering you. It was my mistake. I expected current partition extend somehow. fdisk is the right solution to create 8e partition on free space before playing with LVM.

Andrej