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Re: Software RAID and drive failures

On Sun, 2003-03-09 at 16:48, Massimiliano Ferrero wrote:
> Calyth wrote:
> > I'm no expert comparing to the other people here who've experimented the 
> > whole thing out, but I'd think that you might want to get at least 3 IDE 
> > drives and set up RAID 5 instead.
> I'm no expert either nor I want to start a religious war ;) but...
> RAID 5 had much more sense when the cost of disks was huge.

For a home power user who does things like video capture/editing/etc,
maybe RAID doesn't make as much sense anymore, but:

RAID5, RAID0 & RAID10 still makes sense:
1. In "enterprise" situations, the size & quantity of files is growing 
2. In the SCSI/FC world, big disks are still very expensive.
3. Speed still means spreading IO across many spindles.  That means
   RAID0, RAID5 & RAID10.

> RAID 1 has better performance for reads and small writes, while RAID 5 
> is faster for large writes.

I totally disagree.  RAID5 has to do CRC calculations, and RAID1

Only if you stuff a high-quality storage controller with *lots* of cache
RAM (like in the 512MB-1GB range) will the performance of RAID5 match
that of RAID1.

> RAID 1 has the best redundancy, while RAID5 can take one failure for 
> array (I wouldn't go over 5 disks for array).

??????  RAID1 can only handle 1 failure also!!

If you are a decent administrator, you'll act when a disk becomes
flaky, or as soon as it fails.  (Of course, if 2 disks go at the
same time, you're hosed, but that's the case for RAID1 also...)

| Ron Johnson, Jr.        mailto:ron.l.johnson@cox.net          |
| Jefferson, LA  USA      http://members.cox.net/ron.l.johnson  |
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