Date: Mon, 12 Mar 2001 14:06:36 -0800 From: Alfred Perlstein <bright@wintelcom.net> To: Kevin Oberman <oberman@es.net> Cc: Soren Schmidt <sos@freebsd.dk>, mobile@FreeBSD.ORG, stable@FreeBSD.ORG Subject: Re: Disk I/O problem in 4.3-BETA Message-ID: <20010312140636.A18351@fw.wintelcom.net> In-Reply-To: <200103122146.f2CLkLs08952@ptavv.es.net>; from oberman@es.net on Mon, Mar 12, 2001 at 01:46:21PM -0800 References: <200103122036.VAA99695@freebsd.dk> <200103122146.f2CLkLs08952@ptavv.es.net>
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* Kevin Oberman <oberman@es.net> [010312 13:46] wrote: > Soren, > > Thanks for the quick reply! And right on the button, too. > > I have turned the write cache back on (any relevance to "write cache" > being abbreviated to "WC"? :-) and the time to dd the slices went back > to 10 and 5 minutes (actually 489 and 287 seconds). > > How serious is the possible corruption issue, anyway. The loss in > performance is pretty drastic although it may be that dd is an > especially bad case, but I really don't like to corrupt my disks, > either. If basically running with blind write caching turned on is akin to running your filesystem in async mode. This is because write caching gives the drive license to lie about completing a write, the various ordering of writes are effectively bypassed. If you crash without these dependancies actually written to the disk, when you come back up you have a good chance of losing large portions of your filesystem. -- -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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