From owner-freebsd-questions@FreeBSD.ORG Fri Dec 12 15:02:19 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 B4E8B16A4CE for ; Fri, 12 Dec 2003 15:02:19 -0800 (PST) Received: from dan.emsphone.com (dan.emsphone.com [199.67.51.101]) by mx1.FreeBSD.org (Postfix) with ESMTP id B156D43D31 for ; Fri, 12 Dec 2003 15:02:18 -0800 (PST) (envelope-from dan@dan.emsphone.com) Received: (from dan@localhost) by dan.emsphone.com (8.12.10/8.12.10) id hBCN2GJB079329; Fri, 12 Dec 2003 17:02:16 -0600 (CST) (envelope-from dan) Date: Fri, 12 Dec 2003 17:02:16 -0600 From: Dan Nelson To: Jonathan Wright Message-ID: <20031212230216.GB17799@dan.emsphone.com> References: <5.0.0.25.2.20031212153110.02916768@wheresmymailserver.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5.0.0.25.2.20031212153110.02916768@wheresmymailserver.com> X-OS: FreeBSD 5.2-BETA X-message-flag: Outlook Error User-Agent: Mutt/1.5.5.1i cc: freebsd-questions@freebsd.org 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 23:02:19 -0000 In the last episode (Dec 12), Jonathan Wright said: > up" if there is a delay in the host computer's data access. However, > I am getting inconsistent information on the variable blocksize > setting in mt and don't know if I should use it or not. One site I > found said that variable blocksizes allow the drive to write blocks > at a size that it thinks will be best for the data speed at hand, > while another site said that it allows the drive to use the blocksize > being sent to it from the backup application (making 10,240 byte > blocks in the above tar example). Who is right, or have I got this > all mess up? :) variable blocksize means write data to tape using whatever size chunks the user write()s. I think only ancient QIC tapes actually need you to set a fixed blocksize via mt. > Also is there a preferred blocksize for DDS-3 DAT drives? I use 64k for everything. -- Dan Nelson dnelson@allantgroup.com