SYSMAN permanent exclusion list

[Martin Walker]

We have a CentricStor virtual tape library which presents loads of drives to VMS (there is one drive per disk). There are several systems and there is a virtual tape drive for each disk - all virtual drives are presented to all systems on site. I would like to prevent VMS from automatically configuring the virtual tapes which are not relevant to each node.

It seems that I could use SYSMAN IO SET EXCLUDE for the tapes I don't want to see into SYCONFIG.COM.

My questions are :-

1) How could I then make a drive available to another node should I need to do so?
2) How can you clear the Permanent Exclusion list? Does it survive reboots? (Where is it stored?)
3) Does the exclusion list work for FC tape drives ($2$MGAnnn)? (The help says "You cannot use the SYSMAN IO SET EXCLUDE command to exclude ... Fibre Channel class-driver devices (PG, DG, GG)" - MG is a FC device but is not listed).

I know an easier way may be to just SET DEVICE/NOAVAILABLE but I would like to consider all the options first.

(VMS/Alpha v7.3-2)

Thanks!

[Ian Miller.]

could you do zoning on the FC switch so that the systems do not see the FC tapes

[John Gillings]

Seconded!

If access to devices should be limited, that should be done at the SOURCE, rather than the destination(s).

Consider, by doing it at the source, you have ONE place to define who sees what. Doing it at the destinations means you have N places to define the same stuff and N*(N-1)*(number of devices) ways they can be inconsistent (which, even for small numbers, is a lot more than ZERO). At the source, the configuration can be wrong, but it can't be inconsistent.

Further, think about adding new virtual drives and tapes, then having to propagate the changes N times, or adding new destinations, and copying your configuration.

If at all possible, you should define your devices as "visible to authorised nodes only". This minimises changes required if new nodes are added.

[Murali L.R.]

Hi,
My two cents on one question.
>>2) How can you clear the Permanent >>Exclusion list? Does it survive reboots
>>(Where is it stored?)

I think permanent exclusion list will
survive reboot.
Exclude list is stored in SYS$SYSROOT:[SYSMGR]IOGEN$PREFIX.DAT file.

Regards,
Murali

[Colin Butcher]

I'll assume this is one of your customer's systems, so experimenting on-site isn't an easy thing to do.

If each virtual tape drive has its own WWPN, then it's going to be simplest to control access of systems to virtual drives with zoning in the FC switches.

If that's not how the CentricStor controller works (and I'd expect it not to work that way given that it's a VTL, not a physical tape library with multiple physical drives, each with a WWPN), then there should be a "presentation" of any given virtual tape drive to a given host (HBA WWPN) in the VTL controller, in much the same way that a Vdisk is presented to a host (HBA WWPN) by an EVA. If this is how it works (which is what you'd reasonably expect), then all you'd need to do is set up the presentations correctly in the VTL controller so that only the virtual drive you want is presented to the appropriate target system HBAs. You'd need the zoning in the FC switches set so that the VTL controller ports are associated with all the target system HBAs - just like you'd do with an EVA.

It's far better to control what can see what at the VTL or switch end than trying to fudge it at the VMS end. Sure, SET DEV/NOAVAIL will work, but it's nowhere near as effective as minimising the devices actually visible to the target VMS system.

Cheers, Colin (http://www.xdelta.co.uk).

[Art Wiens]

Inclusion / exclusion could be "controlled" on the VMS side by maintaining the desired devices in SYS$SYSTEM:SYS$SYDEVICES.DAT . This is not "foolproof" though if someone with privs runs IO scan and "finds" all the tape drives for you.

Cheers,
Art