Date: Tue, 14 Dec 1999 16:56:54 -0500 From: Mitch Collinsworth <mkc@Graphics.Cornell.EDU> To: Adon <ahwang@fas.harvard.edu> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: DDS-4 set density woes Message-ID: <199912142156.QAA31551@benge.graphics.cornell.edu> In-Reply-To: Message from Adon <ahwang@fas.harvard.edu> of "Tue, 14 Dec 1999 16:11:28 EST." <Pine.OSF.4.10.9912141608360.5936-100000@is04.fas.harvard.edu>
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>it is nominally compressed (gzip default). in the past, i have seen that
gzip(1) says:
The default compression
level is -6 (that is, biased towards high compres-
sion at expense of speed).
I would not call this "nominal".
>the hardware compression can squeeze some bits out of this. however,
>perhaps you are right. i should try the backup without
>hardware compression.
one or the other, not both.
>my real question is concerning 'mt density' command. it seems to do
well your initial message said "my problem is ..." so that seemed like
the obvious issue to address.
>nothing. i also have an exabyte 8mm drive. for that drive, the density
>shows up as simply "default". attempts to change it were also useless.
I'll offer an educated guess, not having actually used a dds4 drive or
even mt on a freebsd box. The dds drives are capable of detecting what
type of tape you give them by looking at the holes on the underside edge
farthest from the hinge. If mt is confused about the tape type I
wouldn't worry too much about that. As far as hardware compression
there are probably only two choices - on or off. You should be able to
control compression from software but it doesn't always work. If by
testing you can determine that turning compression on/off isn't gaining
you anything (with uncompressed files!) then you need to double-check
the switch settings on the drive and at that point start questioning
the software. Hope this helps.
-Mitch
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