All good points given here re: Raid. I just jumped in here to offer a
description of how battery backup works, not to justify my own setup. But I
would agree that RAID 1+0 would be the best all around protection. It also
has the benefit of increasing throughput by adding more disks to the array.

I compromised by putting my transaction log files on RAID 1+0 and the
database files on RAID5 with a hot spare disk. I also back up logs every
fifteen minutes to a second hot spare sql server. I think this is pretty
common. Though still it was not cheap.

Regards
Ken
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