creating VG

[Patrick Chim]

Hi,

This morning I create the VG in our new VA7410. I used the command 'mknod /dev/vg38/group c 64 0x054000' and then create the VG. However, it show the following error

Increased the number of physical extents per physical volume to 4095.
vgcreate: Volume group "/dev/vg38" could not be created:
A volume group is already using this major and minor number.
Please check the minor number of the "group" device file.

Then I manually remove the group file by 'rm' command and recreate the VG using larger minor number by 'mknod /dev/vg38/group c 64 0x380000'. However, when I recreate the VG it show

vgcreate: Cannot open the control file "/dev/vg38/group":
No such device

Does anyone know what was happening ?? Is there a special method to remove the group file ?? BTW, is there a rule to assign the minor number ?

Regards,
Patrick

[John Poff · Accepted solution]

Hi Patrick,

First, your minor number for the group file you made the first time looks a little off. You'll want to make the minor number in the form of 0xHH0000, where HH is a unique hex number for the volume group. The maximum hex value cannot exceed the value of your 'maxvgs' kernel parameter. The default for this parameter is 10 decimal, so the largest group number you can make by default is 0x0a0000. If you are trying to make a group with a minor number of 0x380000, it means your 'maxvgs' kernel parameter must be at least 56 decimal.

You should just be able to use 'rm' to remove a group file. I'd suggest checking your 'maxvgs' kernel parameter and then try making a group file with a minor number under the max value.

JP

[Sridhar Bhaskarla]

Hi,

In 0x123456

The number in the places 12 should be unique. You tried to create a VG with a id occupying the places 2 and 3 which is wrong. That is the minor number for a logical volume.

Next case is good. However, you will need to make sure that you defined your 'maxvgs' kernel parameter more than 56 (hex 38). Then you can use the number 38 to form your minor number. Verify the kernel parameter by

kmtune -l -q maxvgs

Either increase your maxvgs parameter (limit 255) or pick up a unique hexa number less than your maxvgs.

ll /dev/vg*/group

can give you a list of all group files.

-Sri

[T G Manikandan]

Patrick,

Recently posted

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0xa12731ec5e34d711abdc0090277a778c,00.html

[James R. Ferguson]

Hi Patrick:

I'd add one more fact. About 4-8 KB of lockable kernel memory is used for every increment in your kernel's 'maxvgs'. Hence, it is best maintain the lowest ceiling to 'maxvgs' possible.

Regards!

...JRF...