From owner-freebsd-scsi@FreeBSD.ORG Fri Mar 11 23:13:49 2005 Return-Path: Delivered-To: freebsd-scsi@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id E1A8D16A4CE for ; Fri, 11 Mar 2005 23:13:48 +0000 (GMT) Received: from nargothrond.kdm.org (nargothrond.kdm.org [70.56.43.81]) by mx1.FreeBSD.org (Postfix) with ESMTP id 72E9243D1D for ; Fri, 11 Mar 2005 23:13:48 +0000 (GMT) (envelope-from ken@nargothrond.kdm.org) Received: from nargothrond.kdm.org (localhost [127.0.0.1]) by nargothrond.kdm.org (8.12.11/8.12.11) with ESMTP id j2BNDl6Y043451; Fri, 11 Mar 2005 16:13:47 -0700 (MST) (envelope-from ken@nargothrond.kdm.org) Received: (from ken@localhost) by nargothrond.kdm.org (8.12.11/8.12.5/Submit) id j2BNDlsp043450; Fri, 11 Mar 2005 16:13:47 -0700 (MST) (envelope-from ken) Date: Fri, 11 Mar 2005 16:13:47 -0700 From: "Kenneth D. Merry" To: Dan Langille Message-ID: <20050311231347.GA43379@nargothrond.kdm.org> References: <4231D28B.28878.564DFBA1@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4231D28B.28878.564DFBA1@localhost> User-Agent: Mutt/1.4.2i X-Virus-Scanned: ClamAV 0.83/761/Thu Mar 10 14:01:48 2005 on nargothrond.kdm.org X-Virus-Status: Clean cc: freebsd-scsi@freebsd.org Subject: Re: how does the scsi chain work? X-BeenThere: freebsd-scsi@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: SCSI subsystem List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 11 Mar 2005 23:13:49 -0000 On Fri, Mar 11, 2005 at 17:16:59 -0500, Dan Langille wrote: > Hi folks, > > I added the following devices to my computer, all in one SCSI chain: > > sa0: Removable Sequential Access SCSI-2 device > sa0: 20.000MB/s transfers (10.000MHz, offset 15, 16bit) > sa1 at sym0 bus 0 target 6 lun 0 > sa1: Removable Sequential Access SCSI-2 device > sa1: 20.000MB/s transfers (10.000MHz, offset 15, 16bit) > sa2 at sym0 bus 0 target 8 lun 0 > sa2: Removable Sequential Access SCSI-2 device > sa2: 20.000MB/s transfers (10.000MHz, offset 15, 16bit) > > Then I decided to do some concurrent testing. See below for details. > The goal was really to test filling the tape. This exercises both > the drive and the tape (all of which are used). > > Sometimes a single tar takes nearly 4 hours, sometimes it takes only > 75 minutes. > > My question: It doesn't look like the load is shared evenly. Can > someone talk a bit about this? That's a pretty general and wide > question, I know... You might want to look at your media quality. You said that your drives and media are used... In this case you even got a write error. That's pretty indicative of bad media. (Or a drive that needs to be serviced I suppose.) > [root@lux:/home/dan] # date && time tar cf /dev/nsa0 /usr && time > tar cf /dev/nsa0 /usr && time tar cf /dev/nsa0 /usr && time tar c > f /dev/nsa0 /usr && time tar cf /dev/nsa0 /usr && time tar cf > /dev/nsa0 /usr ; date > Thu Mar 10 22:31:57 EST 2005 > tar: Removing leading '/' from member names > > real 75m15.394s > user 0m45.666s > sys 2m31.039s > tar: Removing leading '/' from member names > > real 114m5.702s > user 0m52.549s > sys 2m45.939s > tar: Removing leading '/' from member names > > real 156m18.091s > user 0m51.538s > sys 2m46.858s > tar: Removing leading '/' from member names > > real 119m48.240s > user 0m49.670s > sys 2m45.721s > tar: Removing leading '/' from member names > tar: usr/home/bacula-restores/usr/X11R6/share/locale/bs/LC_MESSAGES: > Write error > > real 195m0.408s > user 0m38.779s > sys 2m13.158s > Fri Mar 11 09:32:26 EST 2005 And you got another write error on this tape: > root@lux:/home/dan] # date && time tar cf /dev/nsa1 /usr && time tar > cf /dev/nsa1 /usr && time tar cf /dev/nsa1 /usr && time tar cf > /dev/n > sa1 /usr && time tar cf /dev/nsa1 /usr && time tar cf /dev/nsa1 > /usr ; date > Thu Mar 10 22:53:40 EST 2005 > tar: Removing leading '/' from member names > > real 103m35.344s > user 0m50.394s > sys 2m44.732s > tar: Removing leading '/' from member names > > real 112m40.647s > user 0m50.555s > sys 2m46.049s > tar: Removing leading '/' from member names > > real 152m45.638s > user 0m52.656s > sys 2m46.040s > tar: Removing leading '/' from member names > > real 201m0.014s > user 0m53.838s > sys 2m51.051s > tar: Removing leading '/' from member names > tar: usr/home/bacula- > restores/usr/src/contrib/ncurses/form/fld_link.c: Write error > > real 93m59.622s > user 0m22.483s > sys 1m8.356s > Fri Mar 11 09:57:41 EST 2005 With a tape, if it can't write in one area, it'll skip down the tape to try to find an area it can write to. So you may just be running into bad areas on the tape. I would recommend buying some new media that is speced to work on those drives, and then try it out. If you still have variable performance and write errors, then you may have a drive problem. Don't forget to run a cleaning tape through if those drives use cleaning tapes. Ken -- Kenneth Merry ken@kdm.org