Re: Fiber channel: Continue to virtualize through vios or not?

["Larry \"DrFranken\" Bolhuis" <midrange@xxxxxxxxxxxx>]

So more than one question in there!

The first obvious advantage is that you require fewer fiber adapters 
with VIOS. If you have 10 partitions you need 10 Fiber adapters to use 
them directly. That of course requires 10 slots and on the smaller 
machines that's an issue. And of course cost of Fiber cards, more fiber 
ports on the switches as well and simply more cables hanging in the 
rack. You might avoid the switch issue if you cable direct to the DD 
from each LPAR but then you also need more ports on the DD.

Then consider that each Fiber card can have from 2 to 4 ports on it. So 
if a four port card is virtualized through VIOS you can connect port 1 
to Partition 1, port 2 to partition 2 etc. Then when you get to 
partition 5, use port 1 again. So you've spread the load across all the 
ports. If you have good knowledge of when backups occur you can do that 
smartly so that no two partitions share a port if they back up at the 
same time.

THen there is redundancy. That requires that you configure multiple 
paths to the library. Don't quote me on the release but that is 
relatively recent for tape, perhaps even 7.4. (Been there for Disk since 
i 6.1) That too is a benefit. It's been long since I configgered a DD 
(we ruled them out at our facilities) but you will likely need to add 
two wwns to the configuration so the DD can see the partition across 
both paths.

	- DrF

On 1/28/2022 9:19 AM, Rob Berendt wrote:
> We are using fiber channel for connecting our VTL only.  No SAN used by our Power systems at this time.  We virtualize disk from a hosting lpar of IBM i to other lpars of IBM i and AIX.
> Right now we have it virtualized via VIOS to our lpars of IBM i.
> We're at IBM i 7.4 with reasonably recent PTF's.
> We have two lpars of vios on each power system.  Vios is used to virtualize Ethernet and Fiber Channel.  We've got redundancy on the Ethernet to where an lpar of vios could go down and we should run fine.  Seems to work ok during testing, like some vios upgrades midweek.
> We never set up redundancy for the fiber channel.  Right now we have the physical cables in there but never got around to virtualizing them from more than one vios lpar.  I guess we figured it wasn't necessary or worth the effort back then.  Now we're second guessing that.  Not so much for redundancy but more for load.  When we are running backups on multiple lpars at the same time the switch is showing the 8gb fc is getting a lot of exercise.
> We're upgrading our VTLs from DD2500's to 6900's (please no sales calls, the new units are already in storage).  This would be a good time for a change.
> How do you do this kind of load balancing?
> Do we need to still use VIOS?  If not "needed" does it still provide an advantage?
>
> Rob Berendt
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