Right, took the plunge and ordered 4 Hitachi 2TB HDS722020ALA330 drives. First I ran the Hitachi Feature Tool 2.11 (heard on the eweb that 2.13 onwards didn't work with this drive so didn't bother checking) on each drive and enabling acoustic management at 128 setting.
Deleted all the shares that I could off the Terastation via web manager then shut down. Had already deleted the array so was running single drive config on all 4 existing drives. Removed drives 2,3 and 4 at the same time and replace these 3 with the 2tb drivess. System booted, then flagged up error lights about the drives but simply went in to the web manager and formatted 2 then 3 then 4 and all errors went away. Powered down, swapped drive 1 with the last new Hitachi and fired up. Got the error light on the drive but again went in and formatted, all perfect. Have told it to go off and build the RAID5 array with the 4 drives and it is doing it currently. Kiss goodbye to 2 days lol! I have pasted in a grab of the status page for anyone interested.
RAID Array Information
RAID Array 1
Status
Checking ( 0.3 % Complete)
Time Remaining
2702.8 Minute
RAID Mode
RAID5
Disk Structure
Disk 1, 2, 3, 4
Total Capacity
5,856,332,224 kbytes (5585.03 GB)
Amount Used
39,132 kbytes (0.04 GB)
Percent Used
0.00 %
File Format
XFS
So there you have it, all workin, yey :)
Cheers,
Nick.