From owner-freebsd-hackers Mon May 28 18:28:35 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from mass.dis.org (mass.dis.org [216.240.45.41]) by hub.freebsd.org (Postfix) with ESMTP id 7ACA837B424 for ; Mon, 28 May 2001 18:28:33 -0700 (PDT) (envelope-from msmith@mass.dis.org) Received: from mass.dis.org (localhost [127.0.0.1]) by mass.dis.org (8.11.3/8.11.3) with ESMTP id f4T1b7B05693; Mon, 28 May 2001 18:37:07 -0700 (PDT) (envelope-from msmith@mass.dis.org) Message-Id: <200105290137.f4T1b7B05693@mass.dis.org> X-Mailer: exmh version 2.1.1 10/15/1999 To: "E.B. Dreger" Cc: hackers@FreeBSD.ORG Subject: Re: brainstorm: "intermediate" disk caching In-reply-to: Your message of "Tue, 29 May 2001 01:23:28 -0000." Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Mon, 28 May 2001 18:37:07 -0700 From: Mike Smith Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG > > Date: Mon, 28 May 2001 19:01:37 -0500 (CDT) > > From: David Scheidt > > [ snip ] > > > If you're really interested in database performance, remember "Spindles > > is good." Spreading your IO load over as many seperate disks, on as > > many independent IO channels as practical will improve performance. > > There's the problem. With RAID 1+0, total the storage of the spindles, > and half of that is usable. With RAID 5, it asymptotically approaches > unity. ... at the same time as your statistical reliability approaches zero. Running more than a small number of disks in your RAID 5 stripe is unwise; typically you'd use RAID 50 (stripes across a set of RAID 5 units, each of maybe 5-10 disks each). Having said all that, RAID 10 is a real performer just now courtesy of 3ware's product offerings; the capacity loss is offset by the cost savings. I'm sure that the storage market will shift again. -- ... every activity meets with opposition, everyone who acts has his rivals and unfortunately opponents also. But not because people want to be opponents, rather because the tasks and relationships force people to take different points of view. [Dr. Fritz Todt] V I C T O R Y N O T V E N G E A N C E To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message