Date: Tue, 13 Mar 2001 01:33:01 -0800 From: Alfred Perlstein <bright@wintelcom.net> To: Mike Meyer <mwm@mired.org> Cc: Helge Oldach <Helge.Oldach@de.origin-it.com>, oberman@es.net, sos@freebsd.dk, mobile@FreeBSD.ORG, stable@FreeBSD.ORG Subject: Re: Disk I/O problem in 4.3-BETA Message-ID: <20010313013301.L29888@fw.wintelcom.net> In-Reply-To: <15021.58386.377695.943846@guru.mired.org>; from mwm@mired.org on Tue, Mar 13, 2001 at 03:10:42AM -0600 References: <20010312140636.A18351@fw.wintelcom.net> <200103130848.JAA08707@galaxy.de.cp.philips.com> <15021.58386.377695.943846@guru.mired.org>
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* Mike Meyer <mwm@mired.org> [010313 01:10] wrote: > Helge Oldach <Helge.Oldach@de.origin-it.com> types: > > Generally I'd say it's not a bad idea to have write caching on the disk > > enabled - assuming that it is decently implemented. BTW, don't SCSI > > disks use write cacheing as well? :-) > > Yes, they do. And it's recommended that you turn it off if you turn on > softupdates. The driver doesn't do it for you, though. Oh great... Perhaps the disk guru's can add some notes to the sfotupdates docco about this? Or did I just miss this? > I'd be interested to know details about why softupdates makes it more > critical to have write caching off. It's always critical to have write caching turned off to ensure filesystem consistancy during an outtage. Having write caching on is like having the disk ignore _any_ filesystem's attempt to do softupdates/logging/delayed-order-writes because the disk _lies_ to the OS about when a write is safely on the disk. -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] Daemon News Magazine in your snail-mail! http://magazine.daemonnews.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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