On Fri, 19 May 1995 12:04:00 CST Ron Thielen 312-702-7612 said:
>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.

Take a look at the newly announced 3590's.  They are slightly more
expensive than 3490E, but they hold 10GB uncompressed.  They can also
be put into a 3494 Automated Tape Library.  We are looking into these.
Compared to 4/8mm, they are large, fast, reliable, and expensive.

Currently we use 8mm drives on a LAGO datawheel.  We back up about 1.5GB
per night on average, and have sufficient disk storage so that the nightly
backups can all go to disk.  This makes performance less of an issue for
backups.  For restores, the users don't mind waiting a few minutes to get
their files back, since they don't do it very often.

Something to consider for 4/8mm is the number of tape drives to get.  The
DataWheel has 2, as do many other robots.  When doing RECLAIM or MOVE DATA
processes, both tape drives are tied up for hours.  This can impact file
recover performance.  We have written a 2nd level Rexx monitor to detect
this and cancel the process temporarily, to allow the file recover to
complete.  It's a big help, but still not perfect.  For any media,
consider the ratio between capacity and performance.  This will give you
a good idea of how long RECLAIM processing will take for a tape.  If the
time is long, consider getting additional drives if possible.  There are
8mm libraries available with > 2 drives.  Not sure about DLT.

..Paul

Paul Zarnowski                     Phone:   607/255-4757
Cornell Information Technologies   Fax:     607/255-6523
Cornell University                 US Mail: 315 CCC, Ithaca, NY 14853-2601