From owner-freebsd-questions Thu Aug 30 18:24:19 2001 Delivered-To: freebsd-questions@freebsd.org Received: from maile.telia.com (maile.telia.com [194.22.190.16]) by hub.freebsd.org (Postfix) with ESMTP id CF9F437B405 for ; Thu, 30 Aug 2001 18:24:06 -0700 (PDT) (envelope-from ertr1013@student.uu.se) Received: from d1o913.telia.com (d1o913.telia.com [195.252.44.241]) by maile.telia.com (8.11.2/8.11.0) with ESMTP id f7UMsax17847 for ; Fri, 31 Aug 2001 00:54:36 +0200 (CEST) Received: from ertr1013.student.uu.se (h185n2fls20o913.telia.com [212.181.163.185]) by d1o913.telia.com (8.8.8/8.8.8) with SMTP id AAA24025 for ; Fri, 31 Aug 2001 00:54:35 +0200 (CEST) Received: (qmail 27180 invoked by uid 1001); 30 Aug 2001 20:07:34 -0000 Date: Thu, 30 Aug 2001 22:07:34 +0200 From: Erik Trulsson To: Kory Hamzeh Cc: Mike Meyer , questions@FreeBSD.ORG Subject: Re: Performance tuning results Message-ID: <20010830220733.A27037@student.uu.se> Mail-Followup-To: Kory Hamzeh , Mike Meyer , questions@FreeBSD.ORG References: <15245.63001.898491.751110@guru.mired.org> <003b01c13178$ad44fa60$14ce21c7@avatar.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <003b01c13178$ad44fa60$14ce21c7@avatar.com> User-Agent: Mutt/1.3.21i Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Thu, Aug 30, 2001 at 10:24:51AM -0700, Kory Hamzeh wrote: > > > > -----Original Message----- > > From: owner-freebsd-questions@FreeBSD.ORG > > [mailto:owner-freebsd-questions@FreeBSD.ORG]On Behalf Of Mike Meyer > > > What's interesting is that IDE write caching helped more than the > > > softupdates. > > > > Why is that interesting? Softupdates caches things in the system > > memory to try and improve performance in a reliable manner. IDE disk > > caching caches things in the disks memory without worrying about > > reliability. One would expect the more reliable mechanism to be > > slower. > > Because I assume that the system buffer cache is larger than the drive's > buffer cache. But the drive's is probably more efficient since it has access to all the internals of the drive. Eg. the real geometry of the drive (which is almost certainly different from teh geometry the drive reports to the OS/BIOS.) > > > > > If you really want the extra speed - and don't care about reliability > > - you can mount your file systems async, softupdates off. If soft > > udpates are on, the async flag to mount is quietly ignored. That > > caches data in the system memory without regard to reliability just > > like the IDE disk cache does. > > > > Why is IDE write caching less reliable than softupdates? They both basically > do the same thing: delay the write. The softupdates code takes care to order the actual writes to the drive in such a manner that the filesystem should always be in a consistent state. The drive's cache system doesn't do that. -- Erik Trulsson ertr1013@student.uu.se To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message