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Date:      Thu, 6 Mar 1997 11:57:00 +1030 (CST)
From:      Michael Smith <msmith@atrad.adelaide.edu.au>
To:        chad@anasazi.com
Cc:        freebsd-stable@freebsd.org, ronr@ds9.anasazi.com
Subject:   Re: Concatenated Disks
Message-ID:  <199703060127.LAA08276@genesis.atrad.adelaide.edu.au>
In-Reply-To: <9703060038.AA00988@chad.anasazi.com> from "Chad R. Larson" at "Mar 5, 97 05:38:16 pm"

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Chad R. Larson stands accused of saying:
> 
> I've read the man pages for ccd(4) and ccdconfig(8), and the code for
> the kernel driver.  Looks like just what I need.

It does a pretty good job, but a farm of disks like that alone won't give
you sizzling news performance.  Depending on what you actually want, you
might want to research the writings of Joe Greco on the toping in the 
hackers mailing list archive (hit the FreeBSD web pages for this).

> Before I dive in to trying to set this up, can anyone give me some
> advice about concatenated disks?  Is this all known to work?  Including
> mirroring and/or RAID5 parity?  What's the maximum size of a
> concatenated disk?  What's the maximum size of a filesystem?

The 'ccd' driver supports mirroring and concatenation (striping).  It does
not do parity, or any of the other performance-degrading things that 
higher RAID levels do; the only way to do those properly is in hardware,
and if they actually mean much to you, RAID hardware is fairly cheap.

As for size, Satoshi (the guy that integrated the 'ccd' driver from NetBSD)
has a farm well into the hundreds of GB (last I saw, could be bigger now)
running as a single filesystem.

> Chad R. Larson (CRL22)                          Brother, can you paradigm?

-- 
]] Mike Smith, Software Engineer        msmith@gsoft.com.au             [[
]] Genesis Software                     genesis@gsoft.com.au            [[
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