Mine is a single drive and has been formatted as a big ext3 partition.
I used GNOME Partition Editor.
Good so far.

If someone is looking for a drive along these lines, I can now recommend :
- Western Digital WDH1CS10000N My Book Home Edition 1 TB USB/Firewire/eSATA External Hard Drive

# fdisk -l /dev/sdd
###################################
Disk /dev/sdd: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdd1 1 121601 976760001 83 Linux
###################################


# dmesg
###################################
[14728.068000] usb 5-2: new high speed USB device using ehci_hcd and address 13
[14728.340000] usb 5-2: configuration #1 chosen from 1 choice
[14728.372000] scsi8 : SCSI emulation for USB Mass Storage devices
[14728.372000] usb-storage: device found at 13
[14728.372000] usb-storage: waiting for device to settle before scanning
[14728.440000] input: Western Digital My Book as /class/input/input12
[14728.440000] input: USB HID v1.11 Device [Western Digital My Book] on usb-0000:00:1d.7-2
[14733.400000] usb-storage: device scan complete
[14733.416000] scsi 8:0:0:0: Direct-Access WD My Book 1016 PQ: 0 ANSI: 4
[14733.440000] SCSI device sdd: 1953525168 512-byte hdwr sectors (1000205 MB)
[14733.452000] sdd: Write Protect is off
[14733.452000] sdd: Mode Sense: 10 00 00 00
[14733.452000] sdd: assuming drive cache: write through
[14733.472000] SCSI device sdd: 1953525168 512-byte hdwr sectors (1000205 MB)
[14733.488000] sdd: Write Protect is off
[14733.488000] sdd: Mode Sense: 10 00 00 00
[14733.488000] sdd: assuming drive cache: write through
[14733.488000] sdd: sdd1
[14733.508000] sd 8:0:0:0: Attached scsi disk sdd
[14733.508000] sd 8:0:0:0: Attached scsi generic sg4 type 0
[14733.800000] kjournald starting. Commit interval 5 seconds
[14733.800000] EXT3 FS on sdd1, internal journal
[14733.800000] EXT3-fs: mounted filesystem with ordered data mode.
###################################