Date: Thu, 07 Jun 2001 23:36:17 -0600 From: Chris Fedde <chris@fedde.littleton.co.us> To: "Ron S Betts Jr" <rojah@qwest.net> Cc: questions@FreeBSD.ORG Subject: Re: Hardware Compression Of Tape Drives Message-ID: <200106080536.f585aHi27341@fedde.littleton.co.us> In-Reply-To: <000401c0efaa$70f3f990$0a01a8c0@rsbetts>
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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
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