Hi Justin, 

The IBM 3500 includes the function to allow you define multiple logical 
libraries. Each gets a virtual view of the handbot. We do not have the HA 
library feature, but my understanding is that if you have one or two handbots 
it does not change the view your backup server sees for the logical library. 

They do have two extra cost features which do come into play. 

The first called ALMS enhances what you can do with the logical libraries. With 
this feature the tape drives assigned to a logical library do not have to be in 
one contiguous block in the library. It also virtualizes the assignment of 
logical slots to physical slots. It also gives you up to 255 virtual i/o slots 
per logical library. 
This feature is a requirement for more and more other features. For example the 
new extended library cards which are a requirement for lto-5 tape drives.

The virtual library control path is a different lun number for fibre cables. So 
the drives are defined using lun 0 and the virtual library control is lun 1. By 
default you can only have one control path in use for a logical library. With 
the control path failover option you can define multiple control path drives. 
But you must use IBM's tape driver for this support. 
As the paths are handled within  the library firmware and the driver software, 
Netbackup knows nothing of the multiple paths. 

There is also an optional  feature to support multiple data paths into a tape 
drive. This requires the newer lto tape drives or the mainframe tape drives as 
you have to have two fibre ports on the tape drive. This also requires the IBM 
tape driver. Netbackup does not know that this feature is in use. 

You can have many more then 8 logical libraries. 



-----Original Message-----
From: veritas-bu-bounces AT mailman.eng.auburn DOT edu 
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of Justin 
Piszcz
Sent: Wednesday, December 07, 2011 7:25 AM
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: [Veritas-bu] Multipath question

Hi,

With an SL8500 you use ACSLS to interface with the robot (there are a max of 8 
handbots in an SL8500).
With an IBM TS3500 you can have two bots but they do not have anything like 
ACSLS, instead if you have two handbots you need to utilize IBM's multi-path 
architecture.

How have folks on the list configured multi-path robots?
I know there's an option in NBU to add two paths for the robot but I've not had 
a piece of hardware to try it on yet.
How does it work?
Is it stable?
Any gotchas or issues?

Justin.
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