I have had this issue for some time but not really paid it much attention.
I have a 4 drive RAID 5 array setup using mdadm.
This was setup and configured on a previous install and was picked up when I re-installed.
Now for some reason when I go into the webadmin, configuration, raid it shows the RAID status as OK but only shows 2 drives.
However when I ssh to the core and run mdadm -D /dev/md0 it shows there is 4 drives.