topic Re: Simultaneous access from two nodes with VMS 7.3-1 and EVA3000 in Operating System - OpenVMS

Simultaneous access from two nodes with VMS 7.3-1 and EVA3000

WilliamSmith11 — Fri, 26 Nov 2004 18:30:16 GMT

Hi I want to know if is't possible to share an EVA virtual disk simultaneusly from two machines a DS25 and a ES45 alphaserver systems.
I mean like I do in a cluster configuration.

Somebody have and idea how to handle this task.

We have a system running vms in cluster and our idea is to do the same with the new devices (AS ds25, AS es45 and EVA3000)

thank you.

RP

Re: Simultaneous access from two nodes with VMS 7.3-1 and EVA3000

Uwe Zessin — Sat, 27 Nov 2004 02:59:40 GMT

Ralph,
if the virtual disk is to be mounted read/write on at least one node - you MUST use VMScluster software on all nodes that mount it.

When a disk is mounted read/write, OpenVMS makes changes to the volume's structure. Those changes get communicated / are being synchronized with other node's activity by using the distributed lock manager in the VMScluster.

If you don't do that - you can be certain to get corrupted volumes. Some weeks ago I successfully demoed this to a customer when I accidently booted a node from the same system disk with cluster software turned off. (don't ask - it was a long day... and yes, I had a BACKUP - not much work was lost, phewww)

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I remember in the early days of dual-ported massbuss disks one of my employer had a 'semi-cluster' (that was VAX/VMS V3.x - VAXclusters were born in V4).

All systems had access to all data disks through multiport disk drives and multiport adapters. Each node had one disk mounted read/write and /NOCACHE - the other nodes mounted that volume readonly. It worked, well, 'most of the time'.

(Our system manager was a pretty clever woman, who wrote jobs so that we users could use this infrastructure to queue print or plot jobs on other nodes - the cluster-wide queue system wasn't born in VAX/VMS V3, either)

Re: Simultaneous access from two nodes with VMS 7.3-1 and EVA3000

Keith Parris — Mon, 29 Nov 2004 16:47:22 GMT

If you can't cluster the two systems, there are still some other alternatives available:

You could use DECnet remote file access through the File Access Listener (FAL) process.

You could use DECdfs software. This provides access to the files on a disk across a DECnet connection between nodes. The Software Product Description for DECdfs is at http://h18000.www1.hp.com/info/SP2878/SP2878PF.PDF

Re: Simultaneous access from two nodes with VMS 7.3-1 and EVA3000

Wim Van den Wyngaert — Tue, 30 Nov 2004 02:07:54 GMT

... or use NFS.