From owner-freebsd-hackers Fri Apr 14 21:56:48 1995 Return-Path: hackers-owner Received: (from majordom@localhost) by freefall.cdrom.com (8.6.10/8.6.6) id VAA26761 for hackers-outgoing; Fri, 14 Apr 1995 21:56:48 -0700 Received: from shell1.best.com (root@shell1.best.com [204.156.128.10]) by freefall.cdrom.com (8.6.10/8.6.6) with ESMTP id VAA26751 for ; Fri, 14 Apr 1995 21:56:47 -0700 Received: from geli.clusternet (rcarter.vip.best.com [204.156.137.2]) by shell1.best.com (8.6.11/8.6.5) with ESMTP id VAA06601; Fri, 14 Apr 1995 21:56:17 -0700 Received: (from rcarter@localhost) by geli.clusternet (8.6.11/8.6.9) id VAA02893; Fri, 14 Apr 1995 21:55:41 -0700 Date: Fri, 14 Apr 1995 21:55:41 -0700 From: "Russell L. Carter" Message-Id: <199504150455.VAA02893@geli.clusternet> To: phk@ref.tfs.com, rgrimes@gndrsh.aac.dev.com Subject: Re: Just how fast can we go... (was: Re: SCSI target) Cc: freebsd-hackers@FreeBSD.org, julian@TFS.COM Sender: hackers-owner@FreeBSD.org Precedence: bulk |> [cc: trimmed to hackers, seems the best place, since we are talking |> about both scsi and 100MB/sec ether :-)] |> > |> > > |> > > > |> > > Well, with 100MB/S ethernet support now being a reality TCP/IP over |> > > SCSI only has an advantage for *wide* scsi controllers. |> > weeeellll, no, there are advandages in being able to transfer |> > 128KB of scatter-gather data in one hit with NO |> > cpu intervention..... :) |> |> ... |> |> The 21040/21140 chips are bus master just like a scsi controller, and |> can infact do some very large scatter-gather's in there own right. | |But you are still limited to the packet-size on the 100mb net... | If you are going to do a "nice little cluster", there is nothing more important than latency. Bandwidth doesn't matter so much, once you get above several user megabytes per second. I am not able to judge how gather-scatter affects things; I do know that nearly all modern numerical algorithms are constructed so that this does not occur. CRI systems for quite some time have had hardware support for gather-scatter and I've never seen an intelligently written code that required it. YMMV. Russell