If we assume 100GB, that's 100 GB * 2^30 (B/GB) * 8 bits /Byte = 858,993,459,200 bits.
If we get 50% throughput from USB 2.0, that's 240 Mbps or 28.5 MBps
So, it would take 858993459200/240E6 = 3579 seconds or 59.7 minutes to transfer the data.
If you assume the hard disk on the other end is fast enough to continuously write the 28.5 MBps, it'll take probably an hour.
If you'd like to make the backup device remote, I'd recommend a NAS device that uses Gigabit ethernet (assuming your PC also has GigE, you have Cat 5/5e wiring, and a GigE switch!). I'm not sure of the throughput you'd get, but 25% seems achievable, which is about 250 Mbps, equivalent to our USB 2.0 calculation - about and hour.
There are some cheap NAS devices (disk enclosures) available now for $60-$150 without disk drive, but these usually support just Fast Ethernet (100 Mbps). These are devices like Netdisk-35, CoolMax NAS, LaCie, Maxtor, NetGear (SC101), and probably some generics. If you get 80 Mbps throughput, you're looking at 2.98 hours on Fast Ethernet - that's still a bit slow.
Without getting into products intended for businesses, the only personal/SOHO NAS devices that support gigabit ethernet I've found are from Infrant, Buffalo, Thecus, Iomega, and Linksys (EFG120). You're looking at around $300 for the Thecus 2100 to around $700 for the Infrant ReadyNAS, Buffalo TeraStation and the Thecus 4100.
None of these units have USB connectivity to a PC - just GigE. When I was shopping I dropped my GigE requirement and went with the CoolMax NAS device - fast ethernet or USB 2.0 connectivity.
Anyway, if you're going for a GigE NAS solution, you'll then shop on: number of drives supported, RAID support, number of logical volumes/partitioning, network protocols (SMB/CIFS, NFS), and of course, cost. The file system types supported seem to be relatively hard coded into the unit, and won't be a factor. Most support FAT32, Buffalo uses XFS on internal drives, and Infrant doesn't say.
If you must have the NFS network protocol, then your only choice is the Infrant ReadyNAS NV unit. In fact, the Infrant device seems to have the broadest protocol support. Infrant also has hot swappable drives - Thecus (4100) does, but Buffalo does not.
The interesting thing about the Thecus devices are that they are the only ones with dual GigE (but are otherwise just a SMB/CIFS, FAT32 device with RAID support).
Tom's Networking has reviews of both the Infrant and Thecus devices.
Linksys and Iomega seem to be at the lower end of the market, supporting only FAT32 over SMB/CIFS, with the only difference between them is that the Iomega unit supports RAID and the Linksys does not.
Hope this helps.
Last edited by MattCarp; 06-03-2006 at 10:10 AM.