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From: se@IKP.Uni-Koeln.DE (Stefan Esser)
Newsgroups: comp.periphs.scsi
Subject: Re: High Capacity Tapes: Exabyte or DAT?
Message-ID: <1991May28.223259.149101@rrz.uni-koeln.de>
Date: 28 May 91 22:32:59 GMT
Article-I.D.: rrz.1991May28.223259.149101
References: <29543@hydra.gatech.EDU> <9850023@hpcpbla.HP.COM> <1991May28.130950@anusf.anu.edu.au>
Sender: news@rrz.uni-koeln.de (Usenet News System)
Organization: Institute of Nuclear Physics, University of Cologne, Germany
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In article <1991May28.130950@anusf.anu.edu.au>, mbl900@anusf.anu.edu.au (Mathew BM LIM) writes:
||> One of our vendors has told me that the 5GByte figure on the capacity on the
|> newer Exabyte drives is achived by on board data compression and that the actual
|> capacity depends on the compressability of your data. So presumably the
|> actual capacity of a tape is anywhere from 2.3GBytes to 5GBytes. Is this
|> true? If it is, does anyone have any figures on what the "typical" capacity
|> is when backing up a "typical" filesystem?
|
NO, its definitly NOT TRUE, that the 5GB Exabyte drives use data compression 
to achive the higher capacity ! The Exabyte 8500 has twice as many 
data heads as the 8200 (8200: 2 data + 1 servo, 8500: 4 data + 1 servo).

Transfer rate and capacity are doubled, independent of your data.

There will soon be  DAT drives with extended capacity using 50% longer 
tapes and data compression technology.

Stefan Esser
-- 
 Stefan Esser,  Institute of Nuclear Physics,  University of Cologne,  Germany
 se@IKP.Uni-Koeln.DE                                           [134.95.192.50]