SUMMARY:Need specs for HP-35480A 4mm DAT TAPE DRIVE

From: Srinivasa R. Yalavarthy (
Date: Wed Jul 12 1995 - 16:03:06 CDT

Thanks for many good people who responded. It's been great. Though I have
got some flames. I am with this mailing list for the last year or so. My
common sense says that it's O.K. to post a problem about HP DAT drive.

Any way, the good thing there are many good people still left on this planet.

Original query:
> Hello! sun-managers!
> I am looking for specs on HP-35480A 4mm DAT TAPE DRIVE,
> especially, how much you can store upto? I was told that 4.8G
> Is that true? Does it have more capacity OR less..:)

David Steiner <>

>From the HP Product Description:
"The capacity fo a 90m cassette is up to 8 gigabytes, provided that streaming
operation is maintained throughout the writing activity. The capacity depends
on the size of the records and the type of data sent from the host; a
of 8 gigabytes assumes a record size of 512 bytes or greater."
Along with the above caveats, the 8 GB capacity assumes the use of hardware
compression (which, BTW, is not compatable with other manufacturers drives;
an important consideration if you are exchanging tapes with someone else.)
My experience:
Without compression: 1.4-1.7 GB
With compression: ~5 GB
Hope this helps.

Niall O Broin x 3619 <>

With 120M DDS-II tapes the 35480A can write in DDS-II format which
gives a capacity (with these tapes) of 4 Gbyte native. They'll quote
you possible compression rates of up to 4 : 1 - reality seems to be
closer to 1.5 -2 : 1. Of course, your mileage my vary.
Kindest regards,
Niall O Broin
Dave Mitchell <>

A "standard" DDS DAT drive (which I presume the 35480A is),
has the following *un*compressed capacity:
60M tapes 1.3Gb
90M tapes 2.0Gb
What you get in the way of compression depends entirely on what it is
you're saving to tape. My experience of using dump(8) on a variety
of disks with system or user files is that I get slightly less than
a 2:1 compression ratio overall, so I might expect to get nearly
4Gb on a 90M tape.
NB, the uncompressed sizes are also approximate, because it depends on
how many rewrites the drive has to do of blocks of data, which itself
depends on how many "dodgy" areas there are on the tape.
Hope this helps,

Kevin West <>

Have you looked into the DLT tape drives, which store 20/40GB of info per
tape. There is the 2000/4000 tape drives. If you would like additional
information, please send your address and I will be happy to pass literature

Jochen Bern <>

90m Tapes have 2 GB uncompressed, up to 8 GB compressed, Average with
Compression 4-5 GB. 60m Tapes scale down accordingly.
                                                                J. Bern

This might be a stupid suggestion, but why don't you contact HP? This is
not an HP information service. Please leave these questions off the
Sun-Managers mailing list.


                Life is short. Cherish it.....

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