View Full Version : Don't go for RAID

Kevin Walsh
2004-12-10, 09:18
Dan Goodinson [Dan.Goodinson (AT) businessobjects (DOT) com] wrote:
> It's like saying "don't buy a frying pan to mow your lawn".
I agree. If you use a frying pan, you can whack your lawn until it all
looks nice and flat, but it'll never look as good as it would if you
used a lawn mower. :-)

Getting back to the "Don't go for RAID" subject for a moment...

1. RAID cannot be used as a replacement for backups, unless you want
to mess about removing and storing hot-swap mirror drives. Doing
this would leave you with no RAID protection against drive failure
while the array rebuilds.

2. Hardware raid is very good for minimising downtime due to drive
failure, as array rebuilds fully automatic in the event of a drive
hot-swap, and you can keep a hot-spare drive in the array for added
protection. Keep a spare RAID card handy because your server will
be down for a long time if it fails.

3. Software RAID is rubbish. It uses far too much CPU and creates a
lot of drama when you need to replace drives; The drives might
hot-swap, but will probably not rebuild until you've jumped through
a load of hoops. Having said that, software RAID can offer some
failure protection for non-critical systems, so I tend to use it
as a "better than nothing" option.

4. Beware of motherboard on-board RAID as it's often no better than
software RAID in its CPU usage and other features. A RAID card
will probably be a lot better and will be easier to replace.

5. You should have a backup strategy that doesn't rely upon RAID,
unless you can master #1, above, and I wouldn't even consider that.

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