managing shared vgs without MCSG

[Pedro Sousa]

hi.

I need to manage two volume groups in two servers.
It's like this:
VG01 will be active, exclusively, on serverA, and VG02 in serverB.
If serverA fails (crash, network, etc.), I want to activate vg01 on serverB and vice-versa.
any ideas on how to do this without MCSG?

tia,
Pedro

[S.K. Chan]

I suppose it is possible but a lot of work would have to be put in to control which VG you would want to activate upon bootup because you do not want the shared VGs to be activated in both systems. The complication can be much more depending on what kind of disk storage (or hardware) are you planning to use for this "pseudo-mcsg" environment. At one point I have done some experiment with a 12H on 2 J-classes but did not quite manage to get it to work. The key is in the vgexport/vgimport scripts that you're going to write in order to manage this.

[Pete Randall]

Pedro,

I'm assuming that your mechanism to share the device between A & B is already in place - a fibre channel switch, perhaps?

Given that, here's the steps I went through:

1. run a make_tape_recovery and do a full backup

2. vgchange -a n vg01 on server A

3. vgexport -p -s -m /tmp/vg01map /dev/vg01

4. copy the map file to the other server

5. mkdir /dev/vg01

6. mknod /dev/vg01/group c64 0x010000

7. vgimport -s -m /tmp/vg01map /dev/vg01

8. repeat above for vg02 on server B

Now, when one of the server fails, everything is ready to go and all you have to do is activate the volume group with
vgchange -a y /dev/vg01


You do have to use extreme caution to avoid activating the volume group on both servers at the same time. The man page claims this can't be done, but I managed to trash a data base when I ended up with it active on both machines.



Pete

[Rizwan Mohammed]

Hi

once you configure as shared vg ,you can use Event monitoring service to monitor the VGs if system gets down ,you can configure to activate the vgs through EMS on the other machine.

Rizwan

[Pedro Sousa]

Thanks for the answers.
Ok. I think it's better to have MCSG to control the vgs on bot systems.
As I need to move it if I have a network problem, and I do not know how to send the comand to the other node on such case (of course I could use the backup lan card to do it, but I think it does not worth the trouble), so I will install and configure SG.

thanks.
Pedro