Re: Must mknod be equal?

 
SOLVED
Go to solution
mogiro
Regular Advisor

Must mknod be equal?

Hi,
I'm going to try to explain you as clearest as I can my environment. I've got 2 machines, A and B connected to a disk array and a third machine connected to another disk array. The disks arrays are synchronized using SRDF.
Machine A mount a vg with one LUN assigned, machine B mount several vg's with several LUN's and machine C must mount all the vg's (mounted on A and B) once splitted the disk arrays to perform the backup over them. vg's on machine C has been created vgexport/vgimporting from the machines A and B.
The question is. The special file group for the vg's must be the same number on source machines (A and B) and on destination machine C? If not, what can happen? I will be no able to mount the vg on C?
I hope been clear...
Thanks in advance!!
7 REPLIES 7
Gary L. Paveza, Jr.
Trusted Contributor

Re: Must mknod be equal?

I don't see why they need to be the same. You can do this and mount the same volume groups on the same machines (machine A to machine A) and this would require that you have different minor numbers for your volume groups.
mogiro
Regular Advisor

Re: Must mknod be equal?

So... what is the utility of the group special file?
TTr
Honored Contributor

Re: Must mknod be equal?

They don't have to be the same. When you mount the split LUNs from the second array to server C, you create the /dev/vgXX folders and the /dev/vgXX/group files in order to do the vgimpot. So as far as server C is concerned, these are regular disk devices and volume groups and have nothing to do with servers A and B.
mogiro
Regular Advisor

Re: Must mknod be equal?

So you wanna mean that the group special file must only be the same if the are on the same disk array?
TTr
Honored Contributor
Solution

Re: Must mknod be equal?

The group file minor must be unique within the same server. It does not matter if you are in the same array or not. You could have something like this

server A, vg01 group=05
server B, vg01 group=05
server B, vg02 group=06
server B, vg03 group=07

Then on server C you could have for each of the volume groups

server C, vg01 group=05 (srv A vg01)
server C, vg02 group=06 (srv B vg01)
server C, vg03 group=07 (srv B vg02)
server C, vg04 group=08 (srv B vg03)
Michael Steele_2
Honored Contributor

Re: Must mknod be equal?

Hi mogiro:

We have this configuration in our data center in several service guard clusters. The minor numbers in the nodes are always identical for non vg00 vgs because they are referencing the same disks. Thus, the -s option in vgimport etc. But the third vg which we use for BCV's is not unique. This is because the disks are not the same.
Support Fatherhood - Stop Family Law
Masud Parvez
Valued Contributor

Re: Must mknod be equal?

If VG's are under cluster then in all node it has to be same.
But for BCV the pair volume can be mount using different VG minor number.