Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261405AbVEPLMm (ORCPT ); Mon, 16 May 2005 07:12:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261478AbVEPLMm (ORCPT ); Mon, 16 May 2005 07:12:42 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:4010 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S261405AbVEPLMk (ORCPT ); Mon, 16 May 2005 07:12:40 -0400 Subject: Re: Linux does not care for data integrity (was: Disk write cache) From: Arjan van de Ven To: Matthias Andree Cc: linux-kernel@vger.kernel.org In-Reply-To: <20050516110203.GA13387@merlin.emma.line.org> References: <200505151121.36243.gene.heskett@verizon.net> <20050515152956.GA25143@havoc.gtf.org> <20050516.012740.93615022.okuyamak@dd.iij4u.or.jp> <42877C1B.2030008@pobox.com> <20050516110203.GA13387@merlin.emma.line.org> Content-Type: text/plain Date: Mon, 16 May 2005 13:12:36 +0200 Message-Id: <1116241957.6274.36.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.0.4 (2.0.4-4) Content-Transfer-Encoding: 7bit X-Spam-Score: 3.7 (+++) X-Spam-Report: SpamAssassin version 2.63 on pentafluge.infradead.org summary: Content analysis details: (3.7 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 1.1 RCVD_IN_DSBL RBL: Received via a relay in list.dsbl.org [] 2.5 RCVD_IN_DYNABLOCK RBL: Sent directly from dynamic IP address [80.57.133.107 listed in dnsbl.sorbs.net] 0.1 RCVD_IN_SORBS RBL: SORBS: sender is listed in SORBS [80.57.133.107 listed in dnsbl.sorbs.net] X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1056 Lines: 24 > and > request that the kernel switches off the drive's write cache in all > drives unless the whole fsync() stuff works (unless defeated by a > "benchmark" kernel boot parameter). I think you missed the part where disabling the writecache decreases the mtbf of your disk by like a factor 100 or so. At which point your dataloss opportunity INCREASES by doing this. Sure you can waive rethorics around, but the fact is that linux is improving; there now is write barrier support for ext3 (and I assume reiserfs) for at least IDE and iirc selected scsi too. Lets repeat that again: disabling the writecache altogether is bad for your disk. really bad. Barriers aren't brilliant for it either but a heck of a lot better. Lacking barriers, it's probably safer for your data to have write cache on than off. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/