From owner-freebsd-scsi Mon Jan 6 07:36:56 1997 Return-Path: Received: (from root@localhost) by freefall.freebsd.org (8.8.4/8.8.4) id HAA11734 for freebsd-scsi-outgoing; Mon, 6 Jan 1997 07:36:56 -0800 (PST) Received: from destiny.erols.com (someone@destiny.erols.com [207.96.73.65]) by freefall.freebsd.org (8.8.4/8.8.4) with ESMTP id HAA11727 for ; Mon, 6 Jan 1997 07:36:51 -0800 (PST) Received: from localhost (jdowdal@localhost) by destiny.erols.com (8.8.4/8.6.12) with SMTP id KAA04537; Mon, 6 Jan 1997 10:34:35 -0500 (EST) Date: Mon, 6 Jan 1997 10:34:35 -0500 (EST) From: John Dowdal To: Andre Albsmeier cc: freebsd-scsi@freebsd.org Subject: Re: put SCSI disk on same controller as DLT or not? In-Reply-To: <199701061322.OAA14038@server.us.tld> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-scsi@freebsd.org X-Loop: FreeBSD.org Precedence: bulk On Mon, 6 Jan 1997, Andre Albsmeier wrote: > Hi, > > don't know if this belongs to -scsi or -hardware or elswhere... > > I'm running 2.2-BETA on a P166 with two Adaptec 2940. I plan to use > amanda to do backups on a DEC DLT which is connected to one of the > two 2940s. Since a lot of files to be backed up come via a 10 MBps network, I > want to use a holding disk where the data is being collcted first and then > written to the DLT (which is significantly faster than the network). > > To optimize performance, I would like to know if I should connect the holding > disk to the same 2940 as the DLT is attached to or to the other one. > > My thoughts are, that if I had both devices on different controllers, the > throughput could be faster since the data is read from one controller > and pushed directly to the other one. > > Maybe someone has already experience with this, or some of the SCSI experts > can give me a small hint... I used to work for the comp sci department at university of maryland [where amanda was written], where they have a couple hundred machines backed up to a 20GB DLT tape on an old DEC 3000 (alpha). The DLT [with compression disabled; using gzip on clients] was able to stream 1500KB/s, The holding disk was an 9GB seagate elite [5400 RPM]. When the dumps were coming in over the network, the tape did not stream [got about 1/2 the maximum throughput] because the holding disk was thrashing from 10 other dumps coming in from other machines at the same time. When the holding disk was otherwise idle, the system streamed the tape. The amanda server had a single Turbochannel [DEC bus] 10mbit scsi controller and 6 devices, but I don't think the machine would have performed much better with two scsi controllers since the disk was seeking itself to death most of the amanda run. There exists a "amanda-users@cs.umd.edu" mailing list for amanda specific questions. To subscribe (stolen from amanda readme) amanda-users The amanda-users mailing list is for questions and general discussion about the Amanda Network Backup Manager. This package and related files are available via anonymous FTP from ftp.cs.umd.edu in the pub/amanda directory. NOTE: the amanda-users list is itself on the amanda-announce distribution, so you only need to subscribe to one of the two lists, not both. To subscribe, send a message to amanda-users-request@cs.umd.edu. John