Limitation with no of VGs

[Patrick Wallek]

Pete - In a nutshell, yes.

Unless the minor number is reworked, which would probably be royal pain in the a**, I don't see any way to allow more VGs.

The hex range of 00 thru FF is all that you have available.

[James R. Ferguson]

Hi:

You only have two digits for a minor number of a device (see 'mknod()'). This number is packed into hexadecimal so you have 256 possible volume group numbers, ranging from 00-255 or 0x00-0xff in hexadecimal!!!

Regards!

...JRF...

[Denver Osborn]

the 1st 2 hex are for the VG, and the last 2 hex are for the LV number... Are the 3rd and 4th fields used for anything? any chance we could see > 255 lvols or 256 volumes w/ lvm?

-denver

[Patrick Wallek]

You must remember that the 0x?????? minor numbers are not used with just LVM.

If you have a look in the /dev/rmt directory you will notice that the minor number for your tape drives uses all 6 characters of the minor number. These are what control density, berkely/at&t behavior, rewind/no-rewind, etc.

The minor numbers are used in conjunction with the major number to determine the behavior of the device.

So, my guess is, that without a major rework of how device files as a whole are handled, and a redo of the major & minor number combinations, you will not see the possibility of more than a 00-FF range for the VG-id in the /dev/vg*/group file minor number.

[amit mehta_2]

Thanks to all of you