From owner-freebsd-questions@FreeBSD.ORG Sat Feb 17 22:13:42 2007 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id D911016A400 for ; Sat, 17 Feb 2007 22:13:42 +0000 (UTC) (envelope-from m.seaman@infracaninophile.co.uk) Received: from smtp.infracaninophile.co.uk (ns0.infracaninophile.co.uk [81.187.76.162]) by mx1.freebsd.org (Postfix) with ESMTP id 4C8B713C442 for ; Sat, 17 Feb 2007 22:13:42 +0000 (UTC) (envelope-from m.seaman@infracaninophile.co.uk) Received: from [IPv6:::1] (localhost.infracaninophile.co.uk [IPv6:::1]) by smtp.infracaninophile.co.uk (8.13.8/8.13.8) with ESMTP id l1HMDLt9011908; Sat, 17 Feb 2007 22:13:21 GMT (envelope-from m.seaman@infracaninophile.co.uk) Message-ID: <45D77DFA.9090504@infracaninophile.co.uk> Date: Sat, 17 Feb 2007 22:13:14 +0000 From: Matthew Seaman Organization: Infracaninophile User-Agent: Thunderbird 1.5.0.9 (X11/20070120) MIME-Version: 1.0 To: Garrett Cooper References: <45D77216.40308@u.washington.edu> In-Reply-To: <45D77216.40308@u.washington.edu> X-Enigmail-Version: 0.94.0.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------enigA3963BCA62F544073DD0DA07" X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-3.0 (smtp.infracaninophile.co.uk [IPv6:::1]); Sat, 17 Feb 2007 22:13:36 +0000 (GMT) X-Virus-Scanned: ClamAV 0.88.7/2591/Sat Feb 17 19:29:32 2007 on happy-idiot-talk.infracaninophile.co.uk X-Virus-Status: Clean X-Spam-Status: No, score=-1.6 required=5.0 tests=AWL,BAYES_00, DKIM_POLICY_TESTING,NO_RELAYS autolearn=ham version=3.1.8 X-Spam-Checker-Version: SpamAssassin 3.1.8 (2007-02-13) on happy-idiot-talk.infracaninophile.co.uk Cc: freebsd-questions@freebsd.org Subject: Re: gvinum with RAID capable SATA card X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 17 Feb 2007 22:13:42 -0000 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigA3963BCA62F544073DD0DA07 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: quoted-printable Garrett Cooper wrote: > Hello, > Motherboards usually don't support more than 2 SATA ports, and sinc= e > SATA is 1:1, I have to invest in a SATA RAID card to get RAID-5 support= =2E > After reading the handbook a bit I came across chapter 19, which > goes into some detail about why and how to the configure one's disks in= > a software RAID with gvinum. However, I'm not sure what mode (if one > exists) that I could put a RAID card in to make the OS see single disks= =2E > So I guess my point is, can I turn off RAID functionality on the > card and make the disks into single, separated disks available via the > disk controller, or is that impossible with a RAID card? > I think the problem lies with my (limited) knowledge of RAID. Most RAID controllers certainly will support acting in JBOD mode.=20 Check the docco before buying. =20 However, if you've got a hardware RAID card, then you'll almost certainly be better off using it for doing RAID5 than doing it in software with gvinum. The RAID card will have hardware to do the parity calculations needed for RAID5 and offloading that from the CPU is a big win. The balance of advantage between hardware and software RAID is not so clear cut for RAID1 or RAID10 (mirror or mirror+stripe). Software RAID is a lot cheaper, can be monitored by native system tools and is pretty much as performant as hardware RAID unless you have a battery backup unit on the RAID card [in which case you can set the card to tell the OS the data is secure as soon as it is in battery backed RAM on the card (which takes nanoseconds) rather than actually written to disk (which takes milliseconds), hence decreasing IO latency enormously]. When buying a RAID card, an important consideration is that there are FreeBSD compatible management tools available -- otherwise, for example, you'll not get alerted to disk problems other than by the onboard alarm buzzer on the card. Cheers, Matthew --=20 Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard Flat 3 PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate Kent, CT11 9PW --------------enigA3963BCA62F544073DD0DA07 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.2 (FreeBSD) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFF134B8Mjk52CukIwRCJn0AJ9G+AyZi9/yu8hK6AdQzTKLeuCBTgCeO87x xELXpJMQTTZtMpjgYetNU+s= =eU5N -----END PGP SIGNATURE----- --------------enigA3963BCA62F544073DD0DA07--