ServiceGuard - Second Cluster Lock Disk on Mirror

[Jasti Kalyan Babu]

I have a 2 node MC/SG cluster (MA and MB).
The nodes are on two floors (1 and 2).
There is only one package in the cluster (PKG).
There are 2 volume groups in a package (VG1 and VG2).
I have two VA7400?s on two floors (1 and 2)
Each of the VG?s is made up of only two LUNs which are mirrored using mirrordisk. (VG1_LUNA, VG1_LUNB (mirror) and VG2_LUNA and VG2_LUNB (mirror))
The two LUN?s in each VG are located on separate VA7400?s.
We are thinking of configuring the cluster as follows

FIRST_CLUSTER_LOCK_VG /dev/vg1
FIRST_CLUTER_LOCK_PV VG1_LUNA (Primary disk in the mirrored VG)

SECOND_CLUSTER_LOCK_VG /dev/vg2
SECOND_CLUTER_LOCK_PV VG2_LUNB (Mirrored disk in the mirrored VG)

My questions are
1) Can I set my CLUSTER_LOCK_PV to the mirrored disk in the cluster lock VG?
2) What would the behavior of the cluster be when the whole of the 1st floor goes down?

I would appreciate any input on this issue.

[A. Clay Stephenson]

Normally dual cluster locks are not a good idea and are intended only in the case that internal disks are used as lock disks so that when a node fails the lock disk fails also.
In your case, I assume you are concerned that all the power would fail to both the lock disk and the node on the first floor. The best answer is to insure that that does not happen by providing a circuit that is powered from the second floor to one of the power supplies in your VA7400. In any event, the second cluster lock option can be used.

[linuxfan]

Hi,

Normally you don't define multiple cluster lock disk and if you have more than 4 nodes then you don't need a cluster lock disk at all.

In your case it is okay if you define the cluster lock disk but if you don't want to use a disk which would be used for application data, then you could have another LUN created that is shared by both the nodes and make this the cluster lock disk.

This is the link for the CLuster lock section in the Managing MC-SG document.
http://docs.hp.com/cgi-bin/onlinedocs.py?mpn=B3936-90045&service=hpux&path=../B3936-90045/00/00/27&title=Managing%20MC/ServiceGuard

-HTH
Ramesh

[Sanjay_6]

Hi Jasti,

You can do the SG setup in the manner you have written. Since you are having a two node cluster, you must have a lock disk. Now since you are talking about the possibility of the whole of first floor going down (if your first floor goes down, will the second stay ?) you still need to have the SG running or vice versa. So you are stuch with a two cluster lock case, i guess.

Now in case the first floor goes down you still have the 2nd lock disk accessible by the system that is active, so you should not have any problem from the SG side. That should be okay.

Do remember to have both the VG's active on the configuration note at the time of applying the SG configuration.

Hope everything turns out to be a piece of cake to you. If i were you i would put into practice this hypothetical scenario by shutting down the box completely on the first floor.

Hope this helps

Thanks

[melvyn burnard]

What you are proposing is an acceptable solution, and in fact this is usually the ONLY time when dual cluster lock discs are recommended, i.e. physical separation such as floors/bulidings etc. This is commonly referred to as a Campus Cluster.
I would still advise trying to get separate power supplies to the VA7400 arrays, to give you as much protection as possible.
Also ensure you are patched to the latest and greatest ;-}