vgextend only allowed to use 16 Physical Volumes

[Matthew Bullock]

I am trying to create a large, striped and mirrored data area. To do this I need to allocate 18 disks to the volume group. However, when I try to add the last two disks, it complains of "too many links". When performin a vgdisplay, I see that the maximum number of physical volumes allowed is set to 16, how can I increase this number to allow for my extra two disks?
Any help would be greatly appreciated.
Thanks in advance, Matt

[Robert-Jan Goossens]

Matthew,

Could you run next command, change your volumegroup number.

# vgdisplay -v vg00 | grep "Max PV"
Max PV 16

Robert-Jan

[Kenneth Platz · Accepted solution]

Matt,

Unfortunately I believe this parameter, maximum PV's per VG, can only be modified at the time you create your volume group (the other REAL gotcha is the maximum number of PE's per PV, which makes it difficult if you try to add larger disks than you had originally created the VG with).

You would need to re-create your VG with the "-p" parameter:

vgcreate -p 32 /dev/vg01 /dev/dsk/cXtYdZ [...]

Hope this helps

[Matthew Bullock]

I have run the command as you suggested, and like you I get the result of:
Max PV 16
It is this figure that I am trying to increase. I have heard that it is possible, but the person who informed of that could not remember the parameter that controls this figure.
Cheers, Matt

[Sridhar Bhaskarla]

Hi Matt,

By default the command 'vgcreate' will set the 'maxPVs' to 16 if you didn't specify a large number while creating the volume group with '-p' option.

At this time, there is not much you can do to extend the volume group. To change this parameter, you will need to recreate the volume group.

A solution is to create another volume group with the additional disks. Make sure you use sufficiently large maxPV, maxLV, extent size Max PE per PV while creating the volume group. Create new logical volumes and copy the data from old VG to new VG. Then youc an destroy the old VG and add them to new VG for mirroring.

However, striping cannot be done once the LVs are created. And also LVM does not support Striping and Mirroring together. At the best you can do is extent level striping but that may not provide enough performance boost.

-Sri

[Steven E. Protter]

The vgcreate command(ie starting over) is the only hope of fixing this:

vgcreate -p max_pv

with the other parameters of course you need to create a volume group.

SEP

[Matthew Bullock]

All done now! Thank you one and all.
I have recreated the vg with the -p option and all is now well.
Thanks again, Matt