Skip site navigation (1)Skip section navigation (2)
Date:      Tue, 30 Apr 2002 10:15:49 -0700
From:      Michael Sierchio <kudzu@tenebras.com>
To:        "James F.Hranicky" <jfh@cise.ufl.edu>
Cc:        Terry Lambert <tlambert2@mindspring.com>, bsder@allcaps.org, freebsd-fs@freebsd.org
Subject:   Re: Non-standard root filesystems
Message-ID:  <3CCED145.6010607@tenebras.com>
References:  <20020429153020.Q16532-100000@mail.allcaps.org>	<3CCEC7D5.D22356A0@mindspring.com> <20020430130128.11428802.jfh@cise.ufl.edu>

next in thread | previous in thread | raw e-mail | index | archive | help
James F.Hranicky wrote:

> "Terry Lambert" <tlambert2@mindspring.com> wrote:
> 
>>As far as software RAID is concerned: it's a bad idea, from a
>>performance perspective; I don't recommend it.  Note that I'm
>>the person who did the original user space RAIDframe port to
>>FreeBSD in the mid 1990's, so I'm not just talking out my butt:
>>the amount of overhead for parity calculation and storage is
>>*considerable*, and makes RAID hardware a *much* better idea.
> 
> 
> Perhaps with RAID 5, but with 0+1 using vinum, wouldn't you
> see an increase with long enough plexes?
> 
> Granted, it's more disks, but it may be cheaper than hardware RAID
> (or not, haven't looked in a while).
> 
> Plus, just a simple two disk mirror for / wouldn't be all that bad,
> considering / shouldn't get heavy write traffic, right?

It's true that RAID 5 is costlier on writes than RAID 1, but
the problem with the comparison between software and hardware
RAID is that the differences are revealed when other-than-normal
operation is in force.  It's really quite something to see
mirror catch-up or parity recalculation on an entire disk
because of crash or replacement -- when under something like
Veritas or Vinum -- might as well take the system offline.

"Cheaper than hardware RAID" depends on your metric, I suppose --
if the initial cost is all you're interested in,  it's cheaper.
Presumably folks use RAID because they're motivated by other
concerns.




To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-fs" in the body of the message




Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?3CCED145.6010607>