From owner-freebsd-hackers Mon May 28 10:48: 4 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from gekko.i-clue.de (server.ms-agentur.de [62.153.134.194]) by hub.freebsd.org (Postfix) with ESMTP id E44D537B422 for ; Mon, 28 May 2001 10:47:59 -0700 (PDT) (envelope-from so@server.i-clue.de) Received: from i-clue.de (automatix.i-clue.de [192.168.0.112]) by gekko.i-clue.de (8.9.3/8.9.3/SuSE Linux 8.9.3-0.1) with ESMTP id TAA01626; Mon, 28 May 2001 19:55:28 +0200 Message-ID: <3B128FB4.70AE7C69@i-clue.de> Date: Mon, 28 May 2001 19:49:40 +0200 From: Christoph Sold Reply-To: so@server.i-clue.de X-Mailer: Mozilla 4.75 [de] (WinNT; U) X-Accept-Language: de MIME-Version: 1.0 To: "E.B. Dreger" Cc: hackers@FreeBSD.ORG Subject: Re: brainstorm: "intermediate" disk caching References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit 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 "E.B. Dreger" schrieb: > > Greetings all, > > I just had a brainstorm... > > I was thinking about database servers with several spindles in a RAID 5 > array. Write performance is inherently disappointing -- which may or may > not be an issue. It is. Even RAID 1 is better than RAID 5 _for_database_use_. For added security, have run a RAID 10 array (basically, a mirrored stripe set). > Would it be worth the trouble to design an "intermediate" cache, whereby > data are quickly written to a spool disk, then to the final destination? > Sort of like softwares that cache CDROMs on HDD... > > My gut feel is that this would be more trouble than it's worth, would not > net any overall performance*reliability (expressed as a product) gain, and > that one might actually realize a p*r decrease. IMHO it would speed up your DB significantly to have it a) run on a RAID 10 array and b) have it run on the raw disk. Two layers of lag reduced (well, for reads it is possibly only one layer). HTH -Christoph Sold To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message