remove a quorum disk when adding a 3rd node to cluster

[Paul Coviello]

ok did I ever think I would get into this deep of a discussion about this, not!

ok let me step back one step and describe the environment...

we have 3 nic cards in each machine one we use as a private lan to a vendor, second one is the main cluster interconnect, the 3rd is for the general lan and a failover for the cluster communications... we actually have a com file that changes the pedriver paths so that we come up as this. we do have the shared SAN disks and local disks for page and swap.

So if that changes anyones thinking let me know...

thanks
Paul

[Keith Parris]

Having 2 redundant LAN connections as your cluster interconnect reduces the risk of a single node being isolated from the other 2, and thus reduces your risk of a partitioned cluster when you don't have a quorum disk and you use REMOVE_NODE to reduce the cluster down to a single node.

Enabling cluster communications on your 1st LAN (but lowering its priority under SCACP so that while PEDRIVER will track its status and availability using periodic Hello packets, it doesn't really actually get used unless and until both of the other 2 links fail, could give you 3X redundancy instead of 2X, reducing the risk even further. But you might consider that to be overkill, especially if you're tracking failures on the existing two paths using LAVC$FAILURE_ANALYSIS.

[Jan van den Ende]

Keith,

I already knew that where I am pessimistic about Murphy's Law (yes, he was an optimist!), I have to admit that you are paranoid about it. (you must have discussed this a lot with Tom Speake, I guess. He was equally paranoid on the issue).

And yes, if your disk communication path can not also function as an SCS path, like a shared SCSI bus, you ARE fundamentally right.
SAN interconnect is a class in its own. It was introduced to VMS NOT supporting SCS, but if my memory serves me well, it does cluster traffic since V7.3-2 (or was it some ECO, or was it intended to, but not yet there. I can not check that right now).

If, however, the path to the disks CAN also function as interconnect (like the good old CI, DSSI, SAN-if-supporting SCS...), then I can not see a way to a partitioned cluster. Teach me if I am not yet pessimistic enough.

Uwe,
not too bad today, made it within 2 hours, thats over an hour better than yesterday.
The way to fight it really is "lean back and enjoy the music"
Getting stressy will not win you 5 seconds, and is very bad for your health!

Cheers.

Join me in a good beer.

Jan

[Keith Parris]

Yes, if the storage interconnect also passes SCS traffic, that would help.

Support for Fibre Channel as a LAN (including cluster interconnect support) is presently slated for VMS version 8.3.

[Wim Van den Wyngaert]

Alternative

Give each node 1 point and keep the quorum disk with 2 votes. Expected botes on 5.

Thus 1 node can start the cluster on his own (if he sees the q disk), no split clusters are possible and the complete cluster can survive a quorum disk loss.

It all depends on what you want.

Wim