From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 2 Nov 2001 15:23:49 -0800 From: Simon Kirby Subject: Re: Zlatko's I/O slowdown status Message-ID: <20011102152349.B17362@netnation.com> References: <87k7xfk6zd.fsf@atlas.iskon.hr> <20011102065255.B3903@athlon.random> <87g07xdj6x.fsf@atlas.iskon.hr> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <87g07xdj6x.fsf@atlas.iskon.hr>; from zlatko.calusic@iskon.hr on Fri, Nov 02, 2001 at 09:14:14PM +0100 Sender: owner-linux-mm@kvack.org Return-Path: To: Zlatko Calusic Cc: Andrea Arcangeli , Linus Torvalds , Jens Axboe , Marcelo Tosatti , linux-mm@kvack.org, lkml List-ID: On Fri, Nov 02, 2001 at 09:14:14PM +0100, Zlatko Calusic wrote: > Thank God, today it is finally solved. Just two days ago, I was pretty > sure that disk had started dying on me, and i didn't know of any > solution for that. Today, while I was about to try your patch, I got > another idea and finally pinpointed the problem. > > It was write caching. Somehow disk was running with write cache turned > off and I was getting abysmal write performance. Then I found hdparm > -W0 /proc/ide/hd* in /etc/init.d/umountfs which is ran during shutdown > but I don't understand how it survived through reboots and restarts! > And why only two of four disks, which I'm dealing with, got confused > with the command. And finally I don't understand how I could still got > full speed occassionaly. Weird! > > I would advise users of Debian unstable to comment that part, I'm sure > it's useless on most if not all setups. You might be pleasantly > surprised with performance gains (write speed doubles). Aha! That would explain why I was seeing it as well... and why I was seeing errors from hdparm for /dev/hdc and /dev/hdd, which are CDROMs. Argh. :) If they have hdparm -W 0 at shutdown, there should be a -W 1 during startup. Simon- [ Stormix Technologies Inc. ][ NetNation Communications Inc. ] [ sim@stormix.com ][ sim@netnation.com ] [ Opinions expressed are not necessarily those of my employers. ] -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/