Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!haven!udel!nelson From: nelson@udel.EDU Newsgroups: comp.arch Subject: Re: *big iron* Message-ID: <24950@louie.udel.EDU> Date: 27 Sep 89 03:05:08 GMT References: <21962@cup.portal.com> <1989Sep12.031453.22947@wolves.uucp> <22130@cup.portal.com> <1989Sep16.044013.429@wolves.uucp> <259@ssp1.idca.tds.philips.nl> <22308@cup.portal.com> <7981@cbmvax.UUCP> <11538@burdvax.PRC.Unisys.COM> <22488@cup.portal.com> Sender: usenet@udel.EDU Reply-To: nelson@udel.EDU () Organization: University of Delaware Lines: 26 In article <22488@cup.portal.com> cliffhanger@cup.portal.com (Cliff C Heyer) writes: > >I'm talking about sustained rates *per job*, not for the *system*. I know >overall throughput is in excess is 100MB/sec. But who makes a disk drive that >does 100MB/sec transfers? The best now is 3-4MB/sec. So when we get right >down to it, a COBOL program reading a file can expect less than 3-4MB/sec on >a mainframe. (The same reasoning explains how a 100 MIPS 4 processor mainframe >can only support 25 MIPS *per job*) > Since we are talking about "*big iron*", let's talk about real big iron. Cray DD-40 disk drives can support >10MB/sec through the operating system (at least COS; I assume the case is also true for UNICOS). And COS also supports disk striping at the user level, so for sequential reads of a file striped across an entire DS-40 disk subsystem (20+ GB, 4 drives) a process can achieve sustained rates of 40MB/sec. Of course, this is for relatively large (~ 0.5MB) reads, but these aren't uncommon for the sort of processing Crays do. Disk I/O is one of Cray's big selling points vs. the Japanese super-computer manufacturers--their machines generally have mainframe (read 4MB/sec) style disk channels. Mark Nelson ...!rutgers!udel!nelson or nelson@udel.edu This function is occasionally useful as an argument to other functions that require functions as arguments. -- Guy Steele