volume group creation

[bassey essien_1]

I having difficulties creating new volume groups on new disk array, the disk capacity is 65Gig, when i choose create from the actions menu on a volume group, i get a message saying
" the command used to create volume groups /sbin/vgcreate, has failed.
the stderr output from the command is shown below. the volume group has not been created, cannot open the control file "/dev/vg18/group",
no such device. my specified disk has been initialized with pvcreate command, i have created other volume groups but "/dev/vg18/group. could it be that i have exceeded the number of VG per system,what is the maximum numbers of VGs.
Any help will be appreciated, thanks.

[Pal Szabo_1]

The number of VG-s is a kernel parameter.(maxvgs)
(In 10.20 is sure)
SAM->Kernel Configuration->Configurable parameters

But i think you didn't exceed this value.Before you create volume groups you should create a group file:
(For example)
1. mkdir /dev/vg09
2. mknod /dev/vg09 c 64 0x090000

(The 0x090000 number has the following format: 0xNN0000
The NN parameter is runs from
00 to maxvgs)

3. pvcreate /dev/rdsk/c1t1d0
4. pvcreate /dev/rdsk/c1t2d0
5. vgcreate /dev/vg09 /dev/rdsk/c1t1d0 /dev/rdsk/c1t2d0




Regards:
Paul

[Darrel Louis]

Bassey,

The procedure Pal described is correct, but don't forget that the major number(0xNN0000)
should be unique.
Read the man page for vgcreate, they have a example on how to create a VG.

Good Luck

[Dave Wherry]

It may be related to maxvgs. I have seen this happen in the past at 10.20.
The value of maxvgs is set to 10. I only have 2 volume groups on the system so I should be able to create 8 more. I tried to create a volume group number 20. It failed with a message similar to what you see. The number, not the count was higher than the parameter and it failed. I was able to create vg10 with no problem.
I do not see this behavior any longer. I assume it was fixed with a patch. I just suggest setting maxvgs much higher and not worry about it. There's really no penalty for having it set high.

[Henry Weldon]

Make sure you have not exceeded the Max VG's specified in the kernel. The other problem may be that there is a limit on how large the following parms can be. I do not know what the max. value is, but if you use values larger than what I have in the following example, you have to reduce one of the other values too.
Max. Physical Volumes = 48
Max. Physical Extents = 10240 (40Gb disk)
MB per Physical Extent = 4

So if you need a larger disk, either reduce the number of physical volumes or enlarge the MB per Physical Extent.

[Todd Bowden]

Question: What is the kernel parameter of maxvgs?

Lets say you have 20 VG's. The major number has a direct impact on the kernel parameter. For instance lets say you had only 2 VG for maxvgs in kernel parameter. What do you think you the major number could be?

Answer the only possible numbers the major number could be for maxvgs=2 is 0x00 0x01. Why? The VG's major number goes in hex order starting with 00. In your reply that you made the major number 20, whould mean that the maxvgs would have to equal 32 or greater.

Hope this expanation helps.