Xref: utzoo comp.unix.aix:600 comp.periphs.scsi:38 Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!ukc!dcl-cs!aber-cs!pcg From: pcg@aber-cs.UUCP (Piercarlo Grandi) Newsgroups: comp.unix.aix,comp.periphs.scsi Subject: Re: Risc System/6000 Summary: The bottleneck is the filesystem and the arm, not the transfer rate Message-ID: <1660@aber-cs.UUCP> Date: 22 Feb 90 15:52:49 GMT Reply-To: pcg@cs.aber.ac.uk (Piercarlo Grandi) Organization: Dept of CS, UCW Aberystwyth (Disclaimer: my statements are purely personal) Lines: 29 In article emv@math.lsa.umich.edu (Edward Vielmetti) writes: [ disk options on the RS/6000 aha, it's an esdi drive that's built in. I wondered. 23ms, 1.3MB/sec transfer is wimpy for a fast machine. In this configuration the machine is going to be seriously i/o bound, without a doubt. Pah. The bottleneck is the filesystem, unless you do asynch io via a raw device. You cannot get more than 600KB per second out of the filesystem in the best of circumstances, and even that is only achieved, as far I know, by the MIPS UNIX. Others top out at around 300KB per second. Better seek times improve things a bit. Multiple drives, with overlapped seek and transfer, improve things much more for a timeshared system. It is here, and not in higher transfer rates (or even seek times) that SCSI wins over ESDI. But the advantage is nonexistent if you have only one drive. If your only worry is single task fast transfer rate (signal/image processing), be prepared to implement something like the Amoeba or Dartmouth or Cray file systems. The problem is software, not hardware. -- Piercarlo "Peter" Grandi | ARPA: pcg%cs.aber.ac.uk@nsfnet-relay.ac.uk Dept of CS, UCW Aberystwyth | UUCP: ...!mcvax!ukc!aber-cs!pcg Penglais, Aberystwyth SY23 3BZ, UK | INET: pcg@cs.aber.ac.uk