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Date: Tue, 29 Jul 2003 13:25:32 -0400 (EDT)
From: Kenneth Culver <culverk@yumyumyum.org>
To: Darryl Hoar <darryl@osborne-ind.com>
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cc: freebsd-questions@freebsd.org
Subject: Re: Calling all raid experts
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> Greetings,
> I need to build a file server for our marketing departments documents
> and images.  I want to use Freebsd.  Since the data is large, and
> backups would be difficult I was wondering if RAID would be a solution.
>
> I thought that RAID 5 would be the ticket, but after reading up on it,
> maybe not.
>
> Isn't RAID 5 the one where if a disk fails, you plug a new one it and it
> regenerates the lost data ?
>
It does that through the use of some checksum data that's spread across
the disks. Reads on raid 5 can be significantly faster than single disk
because data is striped across multiple disks, but writes don't get as
much of a boost because for every write, there are several operations,
including the recalculation of a checksum, and the writing of both the
checksum and data, then a re-reading of them. Writes are usually faster
than single disk writes, but the gain is not nearly as much as with reads.

Ken