Expanding an array on a SCSI RS/12

[Douw van Wyk]

Im running W2K3 Server and Exchange 2K3 server on a 2 node cluster of Netservers LT6000R, and the shared diskspace is located on a SCSI connected RS/12. Currently 2 LUN's exist:
1. Array 0, RAID5, 6X36GB HP drives containing a 10GB partition for the Quorum, and a 163GB partitions for data.
2. Array 1, RAID1, 2X36GB HP drives containing a 30 GB Partition for the Exchange logfiles.

I bought 4 more drives of the same model and would like to expand the capacity of the array(s)to the maximum size using RAID5.

Should I:
1. Break array 1, add the extra 4 drives and then create a RAID5 LUN and move parts of my Exchange database to this drive?
2. Create a third LUN using RAID5 and move only some of the Exchange datafiles to this new drive?

I need the best solution, don't mind moving datafiles around. Any suggestions apreciated.