[ale] backup/restore mail from USB external drive

[Lightner, Jeff]

Right - 2 can be failed in same period which is why RAID 5 (and RAID 1 with only 2 disks) is an issue.

In RAID6 or RAID10 you'd have to have 3 fail in same period before you'd lose data.

However, even in RAID5 I'd think "within 48 hours" wouldn't be a problem so long the first disk was replaced quickly (ideally you have hot spares so it does it automatically).