From owner-freebsd-questions@FreeBSD.ORG Fri Dec 12 15:31:44 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 592F516A4CE for ; Fri, 12 Dec 2003 15:31:44 -0800 (PST) Received: from out001.verizon.net (out001pub.verizon.net [206.46.170.140]) by mx1.FreeBSD.org (Postfix) with ESMTP id B97EB43D09 for ; Fri, 12 Dec 2003 15:31:42 -0800 (PST) (envelope-from mike@pcmedx.com) Received: from duron.pcmedx.com ([4.46.22.189]) by out001.verizon.net (InterMail vM.5.01.06.06 201-253-122-130-106-20030910) with ESMTP id <20031212233142.QAZU25266.out001.verizon.net@duron.pcmedx.com>; Fri, 12 Dec 2003 17:31:42 -0600 Received: from localhost (localhost [127.0.0.1]) by duron.pcmedx.com (Postfix) with ESMTP id 727DAB0CC; Fri, 12 Dec 2003 15:31:41 -0800 (PST) Received: from mike (mike.pcmedx.com [192.168.240.244]) by duron.pcmedx.com (Postfix) with SMTP id B5A87A9F7; Fri, 12 Dec 2003 15:31:40 -0800 (PST) Message-ID: <025101c3c108$2de2c000$f4f0a8c0@pcmedx.com> From: "Mike Maltese" To: References: <5.0.0.25.2.20031212153110.02916768@wheresmymailserver.com> Date: Fri, 12 Dec 2003 15:32:16 -0800 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1158 x-mimeole: Produced By Microsoft MimeOLE V6.00.2800.1165 X-Virus-Scanned: by amavisd (http://www.amavis.org) and f-prot (http://www.f-prot.com) at pcmedx.com X-Authentication-Info: Submitted using SMTP AUTH at out001.verizon.net from [4.46.22.189] at Fri, 12 Dec 2003 17:31:41 -0600 cc: Jonathan Wright Subject: Re: tar, mt backup BLOCKSIZES, variable & fixed question Seagate SDT224000N DDS-3 DAT 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: Fri, 12 Dec 2003 23:31:44 -0000 > If I run mt blocksize 1024, that sets the actual drive to write data in > 1024 byte blocks. If I make an archive with tar with flag -b 20, tar will > format and send 10,240 byte blocks to the tape drive and the tape drive > will then subdivide those into 1024 byte blocks and put them onto the According to the tar manual, you should use a blocking factor that suits the average file size in the archive. It also says that tape and cartridge media likes larger blocking factors, as it will give better throughput and minimize tape and head wear. I use 128 with my DDS2 drive. Also, 20 is the default, so if that's what you want to use you don't need to specify it. Have a look here for more info: http://www.gnu.org/software/tar/manual/html_node/tar_132.html