From owner-freebsd-questions Thu May 17 18:30:18 2001 Delivered-To: freebsd-questions@freebsd.org Received: from wantadilla.lemis.com (wantadilla.lemis.com [192.109.197.80]) by hub.freebsd.org (Postfix) with ESMTP id C113C37B423 for ; Thu, 17 May 2001 18:30:13 -0700 (PDT) (envelope-from grog@lemis.com) Received: by wantadilla.lemis.com (Postfix, from userid 1004) id 581076ACBC; Fri, 18 May 2001 10:59:47 +0930 (CST) Date: Fri, 18 May 2001 10:59:47 +0930 From: Greg Lehey To: Stephen Cimarelli Cc: Marcus Reid , Gabriel Ambuehl , Jonathan Fortin , questions@FreeBSD.ORG Subject: Re: Raid (BEST PERFORMANCE) Message-ID: <20010518105947.D55915@wantadilla.lemis.com> References: <20010517011226.A4473@blazingdot.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: ; from stephen@clari.net.au on Fri, May 18, 2001 at 10:39:33AM +1000 Organization: LEMIS, PO Box 460, Echunga SA 5153, Australia Phone: +61-8-8388-8286 Fax: +61-8-8388-8725 Mobile: +61-418-838-708 WWW-Home-Page: http://www.lemis.com/~grog X-PGP-Fingerprint: 6B 7B C3 8C 61 CD 54 AF 13 24 52 F8 6D A4 95 EF Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: X-Loop: FreeBSD.ORG On Friday, 18 May 2001 at 10:39:33 +1000, Stephen Cimarelli wrote: > On 17-May-01 Marcus Reid wrote: >> On Thu, May 17, 2001 at 04:50:26PM +0930, Greg Lehey wrote: >>> On Wednesday, 16 May 2001 at 22:07:48 -0700, Marcus Reid wrote: >>>> On Tue, May 08, 2001 at 06:22:26PM +0200, Gabriel Ambuehl wrote: >>>>> >>>>> Hello Jonathan, >>>>> Monday, May 07, 2001, 7:08:48 PM, you wrote: >>>>>> Best Performance Raid is a raid 0+1 setup. >>>>>> For example, you got 4 20gb harddrives. >>>>>> You create 2 strips of 2hds eachs, and you mirror them. >>>>>> It will have redundancy and the speed will be as fast as a normal >>>>> disk. It's >>>>>> basically a Raid-1 setup with 2 hard drives per strip instead of one >>>>> to >>>>>> counter write performance hits. >>>>> Some vendors like to call this RAID 10 (hmm. 1+0=10? only if those are >>>>> strings...). >>>> >>>> If I'm not mistaken, there's a difference between 0+1 and 10: one is >>>> striped and then mirrored, the other is mirrored and then striped. It's >>>> supposed to have some bearing on performance, 0+1 being the faster one. >>> >>> I've heard people make this kind of claim. I can't understand what >>> the difference is supposed to be. Can you justify it? >> >> It's something that I read on the qmail list; people were talking about >> the best RAID scheme to use for a very high-volume mail server. I don't >> have anything to offer from personal experience. I'm assembling a new mail >> machine very soon and have to select which level of RAID to use, so I'd >> be interested to hear if there's any truth behind it. > > Raid levels has seen by Mylex as? > Level 0+1 Combines Daid 0 striping and Raid1 mirroring > > Level 10 Combines raid0 striping and Raid 1 mirroring spanned across multiple > drive groups Hmm. Without defining "drive group", this doesn't say very much. > level 30 Combines Raid 0 and raid 3 across multiple drive groups I very much doubt that Mylex implements RAID-3. I suspect they mean RAID-4. RAID-3 is at sub-sector level. > Level 50 Combines Raid 0 and raid 5 across multiple drive groups I wonder how they envisage RAID-5 without striping. > is there some offical body that decided on what level 10,30,50 are, > or do companys make up there own I think many companies make up their own. I've never heard of 30 or 50. I suspect that the distinction between "0+1" and "10" is bogus, though I'm open to further documentation. Greg -- Finger grog@lemis.com for PGP public key See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message