Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watnot!watmath!clyde!rutgers!im4u!suhler From: suhler@im4u.UUCP Newsgroups: comp.arch Subject: Re: shared memory multiproc. question Message-ID: <1513@im4u.UUCP> Date: Fri, 20-Feb-87 02:55:50 EST Article-I.D.: im4u.1513 Posted: Fri Feb 20 02:55:50 1987 Date-Received: Sat, 21-Feb-87 04:11:03 EST References: <76700001@uiucdcsp> <1205@ogcvax.UUCP> <5699@amdahl.UUCP> Reply-To: suhler@im4u.UUCP (Paul A. Suhler) Distribution: na Organization: Univ. of Texas ECE Dept. Lines: 29 Summary: I/O Limits Performance! In article <5699@amdahl.UUCP> chuck@amdahl.UUCP (Charles Simmons) writes: >Seeing how two different people suggested that distributed memory is >inappropriate for multiple users running independent tasks, maybe someone >could tell me why. I find it hard to imagine a problem which is more >partitionable. Since the tasks are independent, each user should be very >happy to have her very own address space. This is true only if the machine has a decent I/O architecture, i.e., enough paths among local memories and disk(s). Imagine trying to squeeze page swaps over multiple inter-node links. The situation with Intel's iPSC isn't much better: a single ethernet linking a single disk with 32 to 128 nodes. Rumor has it that they're well aware of the problem and will fix it in the next incarnation. One visitor to the CS Dept. here described programs and data that took hours to load and minutes to execute, although that's not exactly what you're suggesting. I believe Ncube has a lot of independent I/O paths in their system; does anyone out there have any experience with their machine? FPS's T-Series was to have had a disk farm with its own hypercube connecting the disks and lots of paths up to the processor hypercube. However the rumor a few months ago on this newsgroup was that they'd scrapped the project. Now I hear that John Gustafson (the designer of the T-Series) doesn't work there any more. Does anyone have information on either of these rumors? -- Paul Suhler suhler@im4u.UTEXAS.EDU 512-474-9517