Very Computer

by **g. doog** » Thu, 10 Jan 2002 01:12:27

I currently have one 7133-d40 drawer with 8 9.1g drives in slots 1-8
(defined as one raid5 array with one hot spare in hotspare pool A0)
that is shared between two ha cluster nodes. I now need to add
additional disk space. I have filled the remaining 8 slots (9-16) on
the drawer with similar drives, but am not sure the best cabling
scenario to use. After reading the adapter planning guide (and other
docs) I question whether to:
1) create a second array on the existing loop (which uses the A-ports)
and put
drives 9-16 in a seperate hotspare pool A1 or,
2) create a second array on a second loop by using the B-ports on the
same adapter and put them in hotspare pool B0.

I realize it can be done either way but I would think that two loops
would provide better reponse by splitting the io across two loops.
From the books I get the feeling that for a smaller number of arrays
(1-2) with such few disks that performance shouldn't be a problem
either way. Support says two loops should provide better performance
but probably not enough to notice. Does anyone have any good rules of
thumb to use in these situations?

by **Simon Marches** » Thu, 10 Jan 2002 05:28:14

> I currently have one 7133-d40 drawer with 8 9.1g drives in slots 1-8
> (defined as one raid5 array with one hot spare in hotspare pool A0)
> that is shared between two ha cluster nodes. I now need to add
> additional disk space. I have filled the remaining 8 slots (9-16) on
> the drawer with similar drives, but am not sure the best cabling
> scenario to use. After reading the adapter planning guide (and other
> docs) I question whether to:
> 1) create a second array on the existing loop (which uses the A-ports)
> and put
> drives 9-16 in a seperate hotspare pool A1 or,
> 2) create a second array on a second loop by using the B-ports on the
> same adapter and put them in hotspare pool B0.

> I realize it can be done either way but I would think that two loops
> would provide better reponse by splitting the io across two loops.
> From the books I get the feeling that for a smaller number of arrays
> (1-2) with such few disks that performance shouldn't be a problem
> either way. Support says two loops should provide better performance
> but probably not enough to notice. Does anyone have any good rules of
> thumb to use in these situations?

Support is right - two loops would be better but you probably won't
notice. But the main factor is cabling - remember to have two separate
loops in a single 7133-D40 you must force inline some of the ports and
that's usually not such a good idea.

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