Path: utzoo!attcan!uunet!fciva!dag
From: dag@fciva.FRANKLIN.COM (Daniel A. Graifer)
Newsgroups: comp.misc
Subject: Re: Exabyte (8mm) versus DAT (4mm)
Keywords: Exebyte Backup
Message-ID: <526@fciva.FRANKLIN.COM>
Date: 10 Jul 90 14:08:18 GMT
References: <9007061713.AA01816@stc06.CTD.ORNL.GOV> <1881@proa.SV.DG.COM> <2188@dino.cs.iastate.edu>
Reply-To: dag@fciva.UUCP (Daniel A. Graifer)
Organization: Franklin Mortgage Capital Corp., McLean, Va.
Lines: 38

In article <2188@dino.cs.iastate.edu> hascall@cs.iastate.edu (John Hascall) writes:
>gary@proa.SV.DG.COM () writes:
>}de5@ornl.gov (Dave Sill) writes:
> [... DAT vs 8mm...]
>}The big questions are ...
>} ... and 4) how fast does it backup data.
>
>   [...]
>   According to DEC it looks like their DATs can do a 10 MBytes/min
>   (with a stiff tailwind? :-).  I've heard the 8mm are somewhat
>   faster--does anyone have some real data on either of these?
>
>John Hascall

This weekend, we backed-up about 560MB in slightly over 1 hour on the Exebyte
we bought under the Prime Computer name.  This was on an EXL325 (25MHz '386
MultiBus II, SCSI on the motherboard, not on the MultiBus).  Admittedly, we
need to do some more tuning on the file systems to get them to run optimally.
Unlike our QIC tapes, the Exebyte is so quiet that I cannot determine whether
it is streaming continuously or not.

The file system tuning matters:  Before an earlier tuning, our 60MB QIC tapes
used to require 35 minutes to fill. Now, they take 15-20.  This is doing
backups using the SysV /etc/savecpio script which essentially does a find |
cpio.  The change is obvious; The cartridge tape now streams continuously.

We tried the double-buffering in afio, with no significant improvement.  We
also fooled with the cpio -C parameter before the disk reconfigure, with only
minimal effect.  We haven't tried either of these since the reconfigure on
either the QIC or the Exebyte.

Hope this answers your question.

Dan
-- 
Daniel A. Graifer			Franklin Mortgage Capital Corporation
uunet!dag@fmccva.franklin.com		7900 Westpark Drive, Suite A130
(703)448-3300				McLean, VA  22102