From owner-freebsd-questions Thu Jun 7 22:36:25 2001 Delivered-To: freebsd-questions@freebsd.org Received: from fedde.littleton.co.us (cfedde.dsl.frii.net [216.17.139.141]) by hub.freebsd.org (Postfix) with ESMTP id 85B5A37B403 for ; Thu, 7 Jun 2001 22:36:23 -0700 (PDT) (envelope-from cfedde@fedde.littleton.co.us) Received: from fedde.littleton.co.us (localhost [127.0.0.1]) by fedde.littleton.co.us (8.11.4/8.11.2) with ESMTP id f585aHi27341; Thu, 7 Jun 2001 23:36:17 -0600 (MDT) Message-Id: <200106080536.f585aHi27341@fedde.littleton.co.us> To: "Ron S Betts Jr" Cc: questions@FreeBSD.ORG Subject: Re: Hardware Compression Of Tape Drives In-Reply-To: <000401c0efaa$70f3f990$0a01a8c0@rsbetts> From: Chris Fedde Date: Thu, 07 Jun 2001 23:36:17 -0600 Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Thu, 7 Jun 2001 17:34:47 -0600 "Ron S Betts Jr" wrote: +------------------ | I have a question concerning how to backup my data using hardware | compression. I have Colorado 2.5/5G ide tape device. How do I | 1)backup using HARDWARE Compression WITHOUT using 3rd party software? | 2)if I use hardware compression with tar do I need to enable "z" flag or | would that complicate things? +------------------ I guess that you know that FreeBSD can "see" the device. It should be reported in the output of dmesg or in your /var/log/messages file. Most tape devices default to using their best compression. But often it is hard to tell if they are. You could write data to the tape from /dev/urandom to learn how much data to expect. Running something like dd if=/dev/urandom of=/dev/rwst0 bs=4096 might help you learn how much data to expect to write to the tape. Note that the output of /dev/urandom is not very compressable. In practice you might expect to write around 20% more data. Using the z flag in tar will only be confusing if you forget to use it when you read the tape. -- Chris Fedde To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message