Schneider, John wrote:
> Greetings,
>         My habit in regards to zoning FC tape drives has always been to put
> one host HBA in a zone with all the tape drives it should see, and to have a
> separate zone for each host HBA.  For example, in a situation with 2 host
> HBAs and 10 tape drives, I would have two zones, one with one host HBA and 5
> tape drives, and the other with the other host HBA and 5 tape drives.
> Pretty simple.
>

Which is AFAIK best practise. One zone per HBA if possible, if not, one
zone per system. This is because HBA's (unlike devices) send out scsi
resets (or other stuff) on power-up or init, you don't want one system
to influence the other.

>         But an IBM consultant working here is telling me that the best
> practice is to have a separate zone for each HBA/tape drive pair.  So in my
> example above, I would have 20 zones instead of two.   His claim is that an
> individual tape drive can hang all the other drives if they are in the same
> zone, but not if they are in separate ones.  Has anyone seen this in real
> life?
>

We've never seen this happen, but then again IBM drives may be inferior
in this respect to STK drives (and tell him that, just to troll :))
Really, this is nonsense.

>         This becomes important to me because I am about to put in new SAN
> switches, and he wants me to follow this recommendation.  I have 2 TSM
> servers with 4 HBAs each, 4 NDMP nodes, and 14 tape drives.  Using my
> scheme, I would have 12 zones, with his scheme I would have 56 zones.  That
> seems like a lot of zones, and unnecessarily cumbersome.
>

Do ask your consultant how many zone's the switches can handle, and how
many it can handle efficiently... His views may change. Really I've
never seen anybody recommend anything above one zone per HBA.

>         Is it really necessary to isolate each HBA/Tape drive into a
> separate zone?  Do individual tape drives really hang other drives in their
> zone?
>
> Best Regards,
>
--
Met vriendelijke groeten,

Remco Post

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