How can I format a new USB drive?

Thanks for the response, but there are several problems here.  If the drive is completely new and has no filesystem on it, attaching it to the ReadyNAS via USB does not present the drive in any way for you to format it.  You apparently have to format the new drive on a separate system (e.g. Linux machine or Mac) before you can attach it to the ReadyNAS.

Further, formating it to ext4 via Linux (e.g. Ubuntu) ultimately fails.  While the drive shows up under System->Overview, backing up to it fails after a while.  I get a hundred or so warnings about virus (usually in Junk mail folders on my IMAP server that is getting backed up), and a bunch of files appear to get copied, eventually the backup fails with a message such as:

Backup Status: Fail: Destination is read-only or files/folders could not be created. Check if these files or folders meet the destination file system limitation.

Cannot create file '/media/USB_HDD_6/Music/Rock/Jonny Lang/Lie To Me/Matchbox Jonny Lang.mp3' (error: Read-only file system)!

It appears as if the USB drive has (suddenly?) gone read-only.

I'm going to try again after reformating the drive through the ReadyNAS UI (click on the drive's gear, then Format-> EXT4).  The last time I tried this, the format never completed, but it seems to this time so I'll see if formating it through the ReadyNAS UI fixes the read-only filesystem problem.

FYI, the USB disk is 2T while I've got 909GB free on the ReadyNAS's 2T drives, so there should be plenty of space on the USB drive to complete the backup.