Date: Fri, 01 Feb 2002 12:30:20 -0500 From: dochawk@psu.edu To: "Mike Meyer" <mwm-dated-1012086328.e3f4de@mired.org> Cc: questions@FreeBSD.ORG Subject: Re: spreading system across four fast scsi disks Message-ID: <200202011730.g11HUKI42130@fac13.ds.psu.edu> In-Reply-To: Your message of "Mon, 21 Jan 2002 17:05:28 CST." <15436.40632.383947.819624@guru.mired.org>
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mike mentioned, > Richard E. Hawkins <dochawk@psu.edu> types: > > 4x 9g cheetah 1500rpm U160 scsi drive > > 2x18g cheetah 1500rpm U160 scsi drive > > Anyway, the FreeBSD installation will run across the 4 small drives, > > with the two large drives for catching data as models run. > > But how to divide the four drives? > Don't give swap it's own drive. If you're really thinking about giving > it 9 gig, give it 2.x gig (x should be > 64K of memory so you can get > dumps) on all four drives. This is the part I find odd. The reason I changed from 4 18g to 4x9g + 2x18g was to get the heads in more positions. What I'm not grasping is why I don't save time with a dedicated swap drive. >If you can split the drives across two controllers, even better. That I can do. I assume I put two little and one big drive on each channel? > > What about /var, though? The purpose of the split is so that the heads > > can be in places likely to be used simultaneously. > The second sentence is critical. For swap, the system is smart enough > to interleave swap across multiple disks. Let it do it's thing. Ahh, it can hit multiple swap sections at once, then? > Vinum can do the same kind of thing with data partitions, though you > can't boot off of them. > > Would anything in / oustside of /usr get touched much while a fortran > > program was running? Would /var get touched more than every few > > minutes? > > > > Does it matter anyway? :) > > > > I assume the program will be on /home (which I figure to give all but a > > little of its drive) and relying on libraries (fortran, imsl, etc.) in > > /usr. > /var gets touched every so often. /usr/ will be where most of your > user commands are, and will get read to run them. With your commands > on /home, they will be swapped in from there if needed. > It's really hard to say what to do with the rest of it without knowing > what you're going to be doing with it, though. No, that's wrong - you > ought to give it to me :-). :) I'm still struggling with it getting given to me . . . the purchase order finally arrived yesterday, so I guess that (oncce more!) I'm to within a week or so . . . > For example, the 4x9g cheetas might be 1Gig FS, 2Gig swap, 6Gig /home, > with vinum used to strip /home across the four devices, possibly with > a a mirror as well. The four fs's would be root, /usr, /usr/src and > /usr/obj so that rebuilding the world would scream. When performance matters, I'll be using all or close to all of memory in a very large array or two, running a single instance of a (possibly multi-threaded) fortran program. Each array element is only a few words of memory, and they end up accessed in an essentially random pattern as I either do an optimization (rather extreme dynamic programming) or let the simulated entities interact (genetic algorithms). The models will generally run for hours or days. The two large drives will be used as serial devices at these times, catching data for later analysis. Hmm, when I'm not running models, /usr/src and /usr/obj could live on these drives . . . thanks hawk -- What part of "non-negotiable" didn't you understand? /"\ ASCII ribbon campaign dochawk@psu.edu Smeal 178 (814) 375-4700 \ / against HTML mail These opinions will not be those of X and postings. Penn State until it pays my retainer. / \ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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