If you have say 100Gigs + it would take forever to restore an entire volume, so they will arrange to ship you a hard drive, preconfigured for your server.
The cool thing is that they allow online recovery too, if you lost one single file or some appended data it can be recovered with ease, whereas not so easy with tape, especially single file recovery such as a simply misplaced/accidentally deleted Word doc. And that's IF your tape actually works, god only knows how many 'successful' tape backups are not really successful as they can't recover some files. It's faster to get it from Abacus than to dig through the server for deleted files and restore it.
I don't use it myself, but have many clients who do and they absolutely LOVE it compared to their old drive or tape backup.
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