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Date:      Tue, 2 Apr 96 10:22:10 MET DST
From:      Greg Lehey <lehey.pad@sni.de>
To:        msmith@atrad.adelaide.edu.au (Michael Smith)
Cc:        john@starfire.mn.org, questions@FreeBSD.ORG
Subject:   Re: looking for large-capacity tape recommendations, discommendations, comments
Message-ID:  <199604020942.LAA16326@nixpbe.pdb.sni.de>
In-Reply-To: <199604020137.LAA08733@genesis.atrad.adelaide.edu.au>; from "Michael Smith" at Apr 2, 96 11:07 am

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>
> john@starfire.mn.org stands accused of saying:
>>
>> I am looking for recommendations and user experience with large-
>> capacity (14Gb+) 4mm tape drives.  These are fairly costly items,
>
> 14G?  No such animal.  4mm tape drives go to 4GB.  

4mm tape (DDS) go to 4 GB uncompressed (DDS-2 with 120 m cassettes).
All DDS-2 drives I know of offer compression, which in my experience
gives about 90% more storage (i.e. 7.2 GB), though this is strongly
dependent on the data (gzipped archives take up more space than
uncompressed data of the same size).  People *have* claimed that DDS-2
will offer up to 16 GB, and that DDS-1 (90m tapes, 2 GB uncompressed)
will offer up to 8 GB, but that's so far from normal experience that I
would consider it a lie.

> 4G media are more than twice as expensive as 2G media; unless you
> have a pressing need to put 4G on a single tape the only
> justification for buying a DDS-2 drive is extra speed.

Not so.  I do a nightly backup of 8 GB on one machine.  With DDS-2, I
just do the backup.  With DDS-1, I'd have to get up in the middle of
the night to change the tape.  Yes, the cartridges are more expensive.
Over here, it's DM 10 for a 90m/4GB DDS-1 tape, and DM 28 for a 120m/8
GB DDS-2 tape, both figures compressed.  Compare these prices to, say,
DM 25 for a QIC-525 tape (520 MB), and the DDS-2 prices don't look
that bad.

> The Sony SDT-7000 would be a good buy in that category; it's claimed
> to be capable of over 700K/sec to/from the media (uncompressed) -
> we see around 400K/sec on an SDT-5200 here, and have been very
> happy with it.

How long have you been running it?  BTW, the HP C1533 seems to run at
about the same speed.

>> and we want to make sure that we get one that we'll be happy with
>> the first time.  I know that Exabyte 8500's are pretty good, but
>> of course, that's an 8mm drive.
>
> Exabytes can be temperamental, but well-kept they're very reliable.

So I've been told.

Greg



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