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Disk Enclosures
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HSZ80 expansion plan

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Mike Lievre
Occasional Contributor

HSZ80 expansion plan


I'm dealing with some older storage hardware for my VMS platforms and I'm wondering if someone could provide some clarification on a few things as well as perhaps act as a second set of eyes to my planned config to ensure I'm on the correct track.

First I would like to determine what the difference between the RA7000/ESA10000 subsystem and the RA8000/ESA12000 subsystem. From what I can tell the RA70000 enclosure is a half height rack that contains one BA370 while the ESA10000 is a full height rack that may contain up to two BA370s. From the documentation I've been able to find the RA7000/ESA10000 is usually used with the HSZ70 controller.

Unfortunately I haven't been able to track down much documentation on the RA8000/ESA12000 though what I do have suggests that this is the subsequent generation and used with the HSx80s. It looks to me like both subsystems contain BA370 enclosures so I'm not sure how they differ. I'm working with HSZ80s so I'm hoping the RA7000/ESA10000 documentation I have (EK_SMCPP_UG. A01) is sufficient to config the HSZ80 subsystem.

Currently I have two full height racks with a BA370 enclosure in the top of each rack. Each BA370 has dual HSZ80 controllers. The controller in each BA370 is connected to its own separate adapter on the host in what I believe is transparent fail over mode. At one point these BA370s were in a single rack and connected to two hosts in multi bus failover mode (see attached diagram); however, that configuration was replaced by an EVA5000 and the new configuration is now being used on a system that requires less redundancy.

I'm now at a point where I would like to add more disks to the configuration. In one of the racks I have a BA370 in the lower half, but it only has one HSZ80. From what I can tell an HSZ80 (or redundant pair) will support up to three BA370s (1 master and up to two expansion) using the IO expansion modules on the back of the cabinet and the PVA address switch. I assume that a cable for each of these modules would extend the length of the 6 SCSI busses. My plan is to extend the upper HSZ80 pair to use the lower BA370 in this fashion. Should I be removing the lower HSZ80 entirely since it won't be in use? Is there any reason (or is it even possible) to connect the upper pair of HSZ80s to the lower single HSZ80 instead of using the lower BA370 as an expansion to the upper.

Finally, are there any concerns with the actual install? Should I be able to simply quiet disk access (or shutdown the host/subsystem entirely) and install the cables to extend the 6 buses? At that point should the upper HSZ80s then have sight of the disks in the lower BA370 and will a run config simply add them as available disks in addition to the previous disks/units in use in the upper BA370. Is there any risk of data loss to the current units in the upper BA370?

Any comments, clarifications, or suggestions would be appreciated.


Mark Poeschl_2
Honored Contributor

Re: HSZ80 expansion plan

Mike, your RA7000/ESA10000 docs should work pretty well for both HSZ70 and HSZ80 based arrays. They are pretty much the same - the HSZ80 was just the later generation of the same SCSI back end/SCSI front end controllers. I think there may be some minor differences, but as I recall they were mostly based on ACS firmware revisions.

MA8000/ESA12000 arrays used HSG80 controllers which are SCSI back end/Fibre Channel front end and are a whole different kettle of fish.

Your expansion plan seems basically sound, though I would absolutely have the hosts and storage array completely shutdown while I was messing with the back-end SCSI cabling. After that, yes a simple "RUN CONFIG" should recognize the new disks. Your existing units should remain intact. As always ensure you have a good backup of everything on the array before proceeding with this kind of re-organization.
Mark Poeschl_2
Honored Contributor

Re: HSZ80 expansion plan

My bad - forget what I said in the second paragraph of my response - didn't read your post closely enough. The rest of my response should be good, though.