Hi

I'm not sure what you are trying to describe, but the TS3500 has control paths 
to the library through one or more drives. Each drive has a 4Gbs FC connection. 
Only 1 session from any host can use each drive at a time.

I'm assuming that when u say 4 ports, you mean that you have 4 FC attached 
drives? The control path to the library can be through drive 1, or through all 
drives, but it's only for fail-over, and I really dont see the reason to 
balance the load to the librray control since it's not much data.

The FC connections arent shared between the drives. Each drive has it's own FC 
connection

For the drives, there is no point in trying to loadbalance across 4 drives, 
since each drive can only service 1 host at a time. You cant "stripe" tape 
drives like you do with disks.

I hope that answered your question.

Best Regards

Daniel Sparrman

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Till: ADSM-L AT VM.MARIST DOT EDU
Från: Mehdi Salehi <ezzobad AT GMAIL DOT COM>
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Datum: 03/18/2011 16:56
Ärende: Control unit port load balancing in TS3500

Hi,
Some zOS systems are connected to a FICON switch like SAN40B.
A TS3500 library has a single control unit that is connected to above
switch.
The library has multiple drives and therefore, many backup/restore
operations can be performed concurrently.
Has the control unit the ability to balance the I/O load between its four
ports? Each control unit port is 4Gbps, so 16Gbps is totally available.
Should we expect to have this capacity shared between all systems that are
connected via the switch ?

Thank you.