[rescue] Small RAID array setup

Bjorn Ramqvist v53278 at g.haggve.se
Fri Jun 27 01:19:32 CDT 2003

"C. Magnus Hedemark" wrote:
> > I would prefer security, capacity, and speed, in that order, for the
> > RAID setup.
> RAID 5 is less secure (you can only stand to lose one drive in the
> array) but gives you much more capacity.  In your case, 80% of the
> space would be usable and the remaining 20% would be used for parity.
> Read performance would be fine but write operations will be slow.

The new gig in hardware-RAID is RAID-NG, where they claim that two disks
can fail in a single array, and still get away with the same parity
overhead as in RAID-5. I don't know "secure" I'd call that method, but
some companies claim this.

Many hardware-RAID manufacturers nowadays are incorporating
writeback-caches to defeat the RAID-5 write overhead. In some cases they
refer this to a "RAID-3" approach, but it's still infact RAID-5 with a
big cache for write operations. It works too, until you defeat the
cache, then things will get slow...

This, however, is far more expensive alternatives for a "Small RAID
array setup" than it's worth. Hence, a cheap hardware-RAID card in
RAID-5 should do the job in most cases. As you said, it's depending on
what type of writes you do.


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