ADSM-L

Re: Tape unit question

1995-05-19 14:04:00
Subject: Re: Tape unit question
From: Ron Thielen 312-702-7612 <SYSRONT AT UCHIMVS1.UCHICAGO DOT EDU>
Date: Fri, 19 May 1995 12:04:00 CST
> Hi all,
>
> What kind of tape units you are using for incremental backup and
> EXPORT.
...
I have spent quite a bit of time recently looking at tape drives for
backup operations on some of our RS/6000s.  We're leaning very heavily
toward DLT format as our standard for this kind of use.  Both 4mm and
8mm tape suffer from performance limitations and lack the capacity we
require.  A 3490E has much better performance but limited capacity.

DLT tapes can support 10GB native and 20GB compressed in Compac Tape III
format, or 20GB native and upto 40GB compressed in Compac Tape IV
format.  The higher density units transfer at 1.5MB/second native and
upto 3MB/second with compression.  The lower density units transfer at
1.25MB/second with upto 2.5MB/second.  For comparison, 4mm transfers
nominally at 400KB/second upto 800KB/second, and 8mm transfers between
500KB/second and 1MB/second.  The 4mm and 8mm transfer rates are
usually hampered by the frequent tape repositioning required.  The DLT
units use serpentine recording, more like a 3490 than helical scan.

3490-E drives transfer at higher rates, about 6.5MB/second, but they're
limited to 16GB capacity even with 7 tapes in the stacker and optimal
compression.  They also cost more.

DLT costs start at $4K and go up depending on what you want.  They're
available in single transport models, dual transport models which
automatically mirror in real time, and single and dual transport library
units which can hold upto 560GB.

The two companies I have been talking with for our RS/6000 related
purchases are Cambex in Waltham Mass. and TTi in Anaheim Ca.  Both
companies have agreements with IBM so their drives are covered by
IBM maintenance.

>
> Thanks,
> Ota
>
> To:  [email protected]

 =======================================================================
Ron Thielen <r-thielen AT uchicago DOT edu>
Manager of Operating Systems
Networking Services
The University of Chicago
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