Hardware

I am configuring a StorageTek 5320 Single-headed NAS with an 8Tb CU. I plan to use this as shared stores for our virtual infrastrucutre. I have configure four RAID 5 volumes between 1.4 - 1.6Tb each.

I plan to have multiple small datastores between 150 - 250Gb each (available as sw-initiated iSCSI LUNs)

Now I'm trying to understand the (dis)advantages of configuring:
#1 one large File Volume (1 primary 250Gb and several segments to fill the RAID 5 volume) or
#2 multiple File Volumes (1 per datastore, matching the intended size)

I think the main disadvantage #1, is the segment association with primary means its much more difficult to re-configure storage (I'd have to re-configure the WHOLE 1.6Tb RAID volume. Is this right?)
Manageability is a little more involved with #2 b/c I'll have 4 RAID LUNs, n number of File Volumes and n number of iSCSI LUNs

Is there a performance advantage either way? What about locking/scsi reservations (I believe this is at the iSCSI level rather than the File Volume, right?)

Thanks for any assistance