5TB raid

[Lennart Sorensen]

On Wed, Apr 16, 2008 at 01:37:24PM -0400, Tyler Aviss wrote:
> (make a third copy if they request...raids do not prevent operator errors)
> 
> I know a few people who have been of the opinion that RAID=invincible.
> Unfortunately, it still doesn't save you from the almight mistyped
> path in an "rm -rf" command :-)

RAID (except 0) is protection for disk failure.  No more, no less.  It
is not protection from bugs, user errors, power failures, random memory
corruptions, etc.  It is NOT a backup system.

It does mean if a disk fails you can keep working and replace the faulty
disk without having to go through much downtime or having to deal with
rebuilding the system from scratch with restore of the data from your
backup.  So it saves you from unexpected downtime due to disk failures.
If you put multiple disks on a single BUS (like parallel scsi) then a
cable failure will still probably take out the raid or at least cut off
access.  So will a controller failure in some cases.  Fortunately the
most common failure seems to be the disk in a working system.  SAS is
much better since it uses point to point links (just like SATA) and is
dual ported so each drive can connect to two controllers at the same
time for redundancy that way.  Still only one power connector though.

Why do people not understand this? :)

-- 
Len Sorensen
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