To update the Key Largo/Key Biscayne firmware in Linux, extract the 
8k_11844.tgz file in a directory and copy the arcconf file from
the ServeRAID 8.40 support CD (in the linux_86_64/sas/cmdline
directory) into the same directory the firmware files were 
extracted into.  Next, run

echo y | ./arcconf ROMUPDATE 1 AS4810

The system will have to be rebooted after this.

To check the firmware version, run

./arcconf GETVERSION