[CentOS] Missing SDLT600's

Hi All,
I have a CentOS5.2 server using a Qlogic QLE220 HBA, connected to 
Quantum DX30  and M1800 libraries via a Qlogic SANbox 5600 switch.  I've 
installed the latest (v8.02.14) drivers from Qlogic for the HBA

The issue I have is I am missing 2 of the 4 SDLT drives provided by the 
M1800 Library.  The DX30 provides 6 drives, which are listed in dmesg 
and assigned /dev/st0->5. I would expect the SDLT's to be st6->10 but I 
only see up to st7 and dmesg only lists 2

Using the QLoigic SAN Surfer software all the LUN's/devices are visible 
to the host.

FYI, I also have an old Sun220R connected to this same switch with a 
qlogic card; Solaris 9 has no trouble seeing all LUNs and devices.

I've "googled" for a fair while and have not see anything that helps. My 
FC knowledge on CentOS is limited so any help with troubleshooting this 
would be greatly appreciated.

TIA
Dan