I would not say we have experience beyond the fact that the Sun leadville 
stack with the qlc cards allows very very little scope for tuning.

There is one document I found on the subject entitled:

"San Foundation Suite Tunables
The Sun StorEdge? SAN Foundation Suite:
Optimizing for performance and fail-over
An Executive Technical White Paper
June, 2004"

You will see there is not much you can change.

>From what I've read about the Emulex driver for the Leadville stack, it 
does still give you access to some of the Emulex driver parameters.  I 
don't yet have a system set up to test this driver, as it requires a newer 
SAN kit than we use as standard.

If you use the 'real' Qlogic (qla2300) and Emulex (lpfc) drivers you do 
get a lot of control, but we cannot use those for various internal support 
reasons - primarily that adding and removing LUNs tends to require a 
reboot.

I would certainly consider using different types of HBA for disk and tape, 
just so you can tune them separately.   We strongly suspect that the qlc 
driver is not ideal for tape (well it must be an issue as at least one of 
our tape vendors only supports it under duress).

The broad principle would be that the disks need a deeper IO request queue 
than is sensible for tape, and that as tape is not usually multipath the 
timers for failover are long for tape, and very very short for multipath 
disk.  EMC provide good documents on how to set up Clariion or Symmetrix 
disk for all sorts of HBAs, but I did note that the Qlogic document was 
for qla2300, not qlc!

If you do find out much, please share it as we would like to learn more.

William D L Brown