I have a SAN in production for disk access and we are looking at adding
fibre tape drives to the setup, initially driving these devices from a
single storage node and thereafter doing LAN-free backups (i.e. installing
additional storage nodes) on some larger hosts over time.  Today I have 2
distinct SANs which are mirror copies of each other for availability, and
have zoning implemented so that only hosts of a given OS type can see each
other and their storage ports.  Tech environment includes: IBM ESSs, AIX,
Solaris, Win2k, Netware, and coming soon 6 x IBM 3590H and 6 x IBM LTO-2
drives.

In order to add tape devices to the SAN I have some questions:

1) Is it wise to mix disk and tape on the same SAN?  My initial reaction is
why not if you zone correctly, but perhaps there are other issues?

2) Can the HBAs in our hosts be used for both disk and tape access?  Again,
my initial reaction is why not but perhaps there are other issues?  Is the
answer different for each OS and if so which are OK and which not?

I would prefer to share as much infrastructure between disk and tape as
possible and I suspect with proper zoning the same fabric can be used for
tape and disk.  If the case is however that I can't share the existing HBAs
and need to add a 3rd HBA for tape use I have to pick which SAN (A or B) to
plug it into, or I have to add a 4th HBA to get visibility to all the
drives.  At that point the complexity (i.e some drives/hosts on one SAN and
some on the other) suggests leaving SAN A and SAN B in place for disk, and
creating a SAN C for tapes.  Creating SAN C however has significant costs
(more switches, more HBAs) and would need good justification.

Fellow NBUers, what would you do in my shoes?

Kind Regards,
Chris