topic Re: mounting disk cluster wide in Operating System - OpenVMS

mounting disk cluster wide

Scotty HD — Fri, 18 Feb 2011 16:44:54 GMT

are these two the same

from one node,
$mount/cluster {disk} {label}

from all node,
$mount/system {disk} {label}

Scotty

Re: mounting disk cluster wide

Hoff — Fri, 18 Feb 2011 16:55:23 GMT

$ HELP MOUNT /SYSTEM
$ HELP MOUNT /CLUSTER

You will want to use a derivative of the MSCPMOUNT.COM template, as that deals with the other case here, which is what happens to your disks when nodes depart and arrive.

See the System Manager's Manual Essentials in the documentation set:

http://www.hp.com/go/openvms/doc

Re: mounting disk cluster wide

John Gillings — Fri, 18 Feb 2011 21:40:30 GMT

Scotty,

They may be the same, but it depends on your disk configuration, and the order that nodes are booted.

For example, in a SAN environment where every node can see every disk independently, mounting on each node makes some sense. However, if some disks are local to a particular node, then boot order matters.

Consider nodes A and B. If A boots before B, A cannot see B's local disks and therefore cannot mount them. If B only mounts the disks to itself, then how will they be mounted on A?

My preference is to use MOUNT/CLUSTER on each node. Mount logic is to check that an expected disk exists:

F$GETDVI(disk,"EXISTS")

if it does check if its mounted

F$GETDVI(disk,"MNT")

if not, mount it /CLUSTER.

If you do this on each node, you can expect a consistent set of disks are mounted after booting nodes in any order.

I also recommend a single, clusterwide shared MOUNT procedure. That way you're guaranteed every node expects and mounts the same set of disks.

Re: mounting disk cluster wide

Scotty HD — Sat, 19 Feb 2011 02:48:10 GMT

Hoff#
John Gillings#
thanks for reply.

i will keep John's comments in mind when i do implementation.

my question is in a way answered that,
lets say cluster has two nodes, A ,B. both are up.
the above two commands would make the disk cluster available and
get synchornized for cluster wide access in the same way.

Scotty

Re: mounting disk cluster wide

John Gillings — Sat, 19 Feb 2011 03:08:23 GMT

Scotty,

If both systems are booted into the cluster, and the disk in question is visible from both nodes, then:

$ MOUNT/CLUSTER

on either node will mount the disk on all nodes in the cluster. It's equivalent to executing the same:

$ MOUNT/SYSTEM

command on each node in the cluster.

The tricky part is dealing with all the combinations and permutations of nodes booting in different orders. It's greatly simplified with SAN storage, as you don't need to worry about visibibiliy of served disks.

Re: mounting disk cluster wide

Scotty HD — Sat, 19 Feb 2011 03:55:15 GMT

thanks to all for help.

Scotty

Re: mounting disk cluster wide

Scotty HD — Sat, 19 Feb 2011 03:56:00 GMT

thanks a lot

Scotty