topic Re: Multiple assignment of same Unit ID in Operating System - OpenVMS

Multiple assignment of same Unit ID

Sean O'Banion at SAIC — Thu, 19 Aug 2010 19:48:21 GMT

What error messages will OpenVMS give when two different SAN storage controllers each have a Unit defined with the same Unit ID?

On a BL860i running OpenVMS 8.3-1H1, two MSA1000s with no zoning where connected with the same Unit ID in use, one of which was the boot volume, but the other was the one being used, so the system would not boot. We eventually figured this out, but looking back, we can’t find any error messages related to this.

Re: Multiple assignment of same Unit ID

Heinz W Genhart — Fri, 20 Aug 2010 15:43:42 GMT

Hi Sean

we had a similar problem. We where migrating from HP XP24000 Storage to EMC.

We had all our XP-San Disks mounted, when the San-Team configured new units on the EMC-San. One unit number of the EMC storage was same as one unit number of the XP storage.
There was no error message as far as I know (another Team Member did this migration).

After the San-Team removed the newly configured EMC unit from zoning, we could mount and use the unit from the XP Storage again as before.

Regards

Geni

Re: Multiple assignment of same Unit ID

abrsvc — Fri, 20 Aug 2010 15:48:17 GMT

My experience has shown that unit ID conflicts often result in not seeing the devices at all. I suspect that the low level hardware can't handle the multiple "responders" to bus queries and ignores the devices.

Dan