Date: Wed, 4 Mar 1998 19:43:16 +0100 (MET) From: Wilko Bulte <wilko@yedi.iaf.nl> To: shimon@simon-shapiro.org Cc: hackers@FreeBSD.ORG, julian@whistle.com Subject: Re: SCSI Bus redundancy... Message-ID: <199803041843.TAA01389@yedi.iaf.nl> In-Reply-To: <XFMail.980303160952.shimon@simon-shapiro.org> from Simon Shapiro at "Mar 3, 98 04:09:52 pm"
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As Simon Shapiro wrote... > > On 03-Mar-98 Wilko Bulte wrote: > ... > > > Drive write caches are Evil. Every write cache without good battery > > backup > > is Evil. Talk to a DBMS guy about enabling disk write caches. Put > > sneakers > > on and be prepared to run fast... > > Nah, we just smile at you and put your reume in the can... And rightfully so :) > Actually, there are ways around that. I promised to make them available on > FreeBSD and I will. Real Soon Now. I am waiting for hardware for > testing... Anxiously awaiting. I just missed an opportunity today to obtain a Mylex DAC960 3 channel RAIDcard. Bah. > > But then again, with VM systems that have megabytes worth of unflushed > > data the best way to loose your data is to pull the plug from your server > > ;-) > > Top said, on last make world that there are 158MB of buffers in use. This > is 5 times the total disk capacity on the first Unix port I tried to > compile. Scary. I had Ultrix-11 running on an PDP11/34 256k mem and 2x RK05. Slow as molasses but it worked. Had a couple of fresh CS weenies watch it in awe. Still have this 11/23 and 11/73 in the basement waiting for a memorable event in Unix history (maybe a major earthquake in Redmond? ;-) > Terry? Any thoughts on hot-starting a Unix based PC? We need to dump > memory quickly, I think. No way to preserve DRAM across BIOS resets I know > of. Assuming we have the ability to dump memory quickly (see below), can > we just snap a state, dump it, leave a signature and resume at power up? > > We had that on VAXes with VMS (Not AT&T Unix, and I do not think BSD). A couple of years ago while working at Philips Info Systems we had a SysV2 derivative that could do powerfail/restart (as we called it). It used some battery backed up RAM, and it was not a PC (M68K cpu). Having never worked on that kernel I don't know how they did it. But it worked pretty well. > Memory SNAP: If you write it into a DPT controller, and the controller has > enough cache to hold it, it is pretty fast. I can sustain about 2us per > transaction overhead and about 120MB/Sec. This gives us about a second or > two. The new DPT's can retain the cache until power returns. > Even a small UPS (with poer alarms will last long enough. But how do you checkpoint things? So, where did the processor leave off? _ ______________________________________________________________________ | / o / / _ Bulte email: wilko @ yedi.iaf.nl http://www.tcja.nl/~wilko |/|/ / / /( (_) Arnhem, The Netherlands - Do, or do not. There is no 'try' --------------- Support your local daemons: run [Free,Net,Open]BSD Unix -- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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