From owner-freebsd-questions@FreeBSD.ORG Tue Aug 26 07:15:02 2003 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id EC40E16A4BF for ; Tue, 26 Aug 2003 07:15:02 -0700 (PDT) Received: from dan.emsphone.com (dan.emsphone.com [199.67.51.101]) by mx1.FreeBSD.org (Postfix) with ESMTP id 0B74343FBF for ; Tue, 26 Aug 2003 07:15:02 -0700 (PDT) (envelope-from dan@dan.emsphone.com) Received: (from dan@localhost) by dan.emsphone.com (8.12.9/8.12.9) id h7QEF0Cp076027; Tue, 26 Aug 2003 09:15:00 -0500 (CDT) (envelope-from dan) Date: Tue, 26 Aug 2003 09:15:00 -0500 From: Dan Nelson To: David Landgren Message-ID: <20030826141500.GH26367@dan.emsphone.com> References: <3F4B1761.8060807@landgren.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3F4B1761.8060807@landgren.net> X-OS: FreeBSD 5.1-CURRENT X-message-flag: Outlook Error User-Agent: Mutt/1.5.4i cc: freebsd-questions Subject: Re: A DLT unit on /dev/sa0 is really slow X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 26 Aug 2003 14:15:03 -0000 In the last episode (Aug 26), David Landgren said: > I have an external DLT tape (a COMPAQ DLT VS 40/80 5133 according to > camcontrol). It seems glacially slow to me. Last night I backed up > many gigabytes of files from a remote machine over NFS. It took over > five hours to do it. My overworked Sun E-450 will do this in a shade > over three hours. > > What is more, the remote machine and my FreeBSD box have gigabit > Ethernet adapters, and both machines, as well as the switch they are > connected to all report 1000baseT full duplex. The sun, on the other > hand, is running 100baseT. > > When I run a "tar t" to list the contents of the archive, the output > is really slow. It's taken about half an hour so far to list the > first 50 or so files (and none are exceptionally big, 10Mb on > average). > > When I listen to the tape drive, I hear it start and stop frequently, > with lots of pauses. I would have expected it to spin continuously. > It is, after all, a *streaming* device. DLTs will only stream if they are fed data at a fast enough rate; otherwise they shoeshine. Try running with a 64k blocksize instead of tar's default 10k ( tar cb 128 ) . -- Dan Nelson dnelson@allantgroup.com