Did you get the output of cat /proc/filesystems ?

Writing a longer reply, but wanted to catch you whiel you were still online

---------- Post updated at 03:18 PM ---------- Previous update was at 02:34 PM ----------

Those help a lot. You've got a single-disk IBM-PC compatible system. There's no worrying about which disk to back up, and the backup you purchased is definitely larger than the disk the server uses. And all the files you care about, your company's data-files, are probably all in /home/, stored in /dev/sda6, nicely separated from the rest.

You've got two options:

A) Offline backup. Turn your server off, boot some backup software, run the backup, reboot, done. It won't be able to serve files while it's backing up.

500 gigs might take 15 hours on a 100baseT network, or even twice that if half-duplex, so I'm not sure a network backup is practical. Too bad, since a udpcast boot CD would make it much easier for you.

Instead I'd suggest booting a gentoo minimal liveCD. The amd64 disk is probably better if your system can boot 64-bit at all (whether your server's OS is 64-bit isn't relevant for an offline backup, just your CPU). You can make your server reboot cleanly by running /sbin/reboot, it may take several minutes as it will try to shut down things in an orderly fashion. When it reboots, make it boot the Gentoo CD, it should boot you to a raw Linux root prompt. From there you can do this:

This will take roughly four to eight hours, I think. In the end you'll have a raw, bare-metal backup; Windows won't be able to use it, but Linux can, and if your server's hard drive dies, you could crack the drive out of your Buffalo's case and expect it to boot normally inside your server. (Assuming, of course, it has the proper connectors.)

There might even be ways to keep the /home partition on it fresh once you make it since your Linux server will still be able to talk to this disk.

B) Online backup. It won't back up the whole server, just your company's datafiles. You may be able to do this with minimal interruption to the server's clients, but, files in use may not be backed up properly.