Extending one VG over two LUN's

[Ade Odimayo_1]

Hi everyone,

My wheel's are spinning concerning an LVM issue and I'd aprreciate any suggestions....

Breify put I'm trying to extend one volume group over two seperate LUN's which reside on a VA7400. I'm not too sure what I'm doing wrong but although I can extend the VG over both LUN's I get the message below (I get a similar output using SAM too).

---
#vgextend /dev/vg30 /dev/dsk/c4t3d1
vgextend: Warning: Max_PE_per_PV for the volume group (6400) too small for this PV (10239).
Using only 6400 PEs from this physical volume.
Current path "/dev/dsk/c5t2d0" is an alternate link, skip.
Volume group "/dev/vg30" has been successfully extended.
Volume Group configuration for /dev/vg30 has been saved in /etc/lvmconf/vg30.conf
---

The VG seems to use both LUN's quite happily - the alternate link is my fault as I did'nt specify the alternate disk, although I don't think this is causing the issue.

Has anyone had this same problem or am I missing something obvious?

I thank you!

Tim

[Pete Randall · Accepted solution]

Tim,

The default max PE's is too small for this size VG. You can change this at vgcreate time.
/usr/sbin/vgcreate [-f] [-A autobackup] [-x extensibility] [-e max_pe]
[-l max_lv] [-p max_pv] [-s pe_size] [-g pvg_name] vg_name
pv_path ...

HTH,
Pete

[Dietmar Konermann]

Tim,

during VG creation the "PE size" and the "Max PE per PV" is configured (either using the vgcreate options -s and -e or by accepting the command's defaults).

Now you try to add a PV to a VG that is configured with too small metrics. LVM warns you that only a smaller part of the PV is used. You would need to re-create the VG with higher values to get this LUN added. Or you could split the LUN and add the space by adding several smaller LUNs.

There is no way to change that metrics for an existing VG.

Regards...
Dietmar.

[Vincent Farrugia]

Hello,

6400PEs are equivalent to 25Gb is the 4Mb PE is used.

How large is the current VG? If it is 103Gb, then you will have exceeded the file system limit of 128Gb.

I'm not certain about this but I think that it's the answer.

Vince

[James R. Ferguson]

Hi Tim:

As already noted, the value of 'max_pe' is limited to 6400 and you are *wasting* (10239-6400) extents of your newly added physical volume.

The LVM geometry is set at the time of a 'vgcreate' and cannot be changed once established. For 'max_pe' the default is the larger of 1016 extents or the number of physical extents found on the disk used during creation.

I suggest that you backup your data, destroy the volume group you are presently using, and recreate it specifying appropriate values for 'max_pe', 'pe_size' and 'max_pv' when you issue the 'vgcreate' command. Have a look at the man pages for 'vgcreate' for more information.

Regards!

...JRF...

[Ade Odimayo_1]

Aha!

Thanks everyone, excellent answers, especially from James.

What we need is a virtual bar so I can buy you all beers!

Cheers,

Tim