RAID 1 does not substitute for backup since a virus/worm/pest wipes out not only one drive but both at the same time. Same story for "accidental" deletes. In fact in 2 decades of watching RAID 1 users I've encountered one and only one save. All the other times the other issues killed the owners which were under some impression that RAID 1 meant they could skip backup.
"Hey, it's realtime backup. Right?"
Nothing further from the truth. RAID 5 is preferred since the array can keep working until you have time to replace the failed drive. It still doesn't protect from the more common failures.
Bob
It seems to me that using a RAID 1 configuration in a small business server is the way to go. If a drive goes down than there is another one there to fall back on, right? Following this logic companies will ALWAYS be up and there is no need for any other RAID configuration. SO . . .
Why are there other RAID configurations?
RAID 5 seems to be the most popular, but why? As far as I can tell there are small gains in performance, so what's the draw?
Looking forward to your replies,
Po

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