I have an F820, 6.4.2P6, with dual port FC card that's getting a lot of scsi timeout msgs on the 7b port.  The scsi timeouts spans all disk shelves on the 7b loop.  All other loop is fine.  These started when I moved the 18GB FC9 shelves from a F880c to the F820. 
 
Working the tech support, I replaced a couple of the LRC, replaced two shelf cable interconect, recheck all the cables, replaced FC card slot 7, remove/reinsert all the drives, and ran fcal check which passed all fcal tests.  The core file result indicated to bug #98110 but upgraded to v6.4.2P6 did not resolve these error msgs.  The filer panic a few times before running v6.4.1 that's why tech support recommends upgraded to v6.4.2P6. 
 
Right now I disconnected the second loop 7b.  Any ideas?
 
Slot:            7b
Description:     Fibre Channel Host Adapter 7b (Dual-channel, QLogic 2200A rev. 5)
Firmware Rev:    2.1.32
PCI Bus Width:   64-bit
PCI Clock Speed: 33 MHz
 
Error Msg:-------------------------------------------------------------------------------------------------------
Sun Oct 26 09:05:30 CST [scsi.cmd.retrySuccess:info]: Device 7b.20: request successful after retry #1: cdb 0x2f:00182000:0400.
Sun Oct 26 09:05:59 CST [ispfc_timeout_4:warning]: 7b.27 (0x0400001b) (0x039a7320,0x2f:00196800:0400,0/0,1157/264/0,19642/0): command timeout, quiescing drive to allow outstanding I/O to complete.
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thanks,

Marcus Bui