Ref: 03250334
Title: Mag Tape Internal Errors; MTBF Rates for Tape Drives
Date: 8/17/88

Copyright 3Com Corporation, 1991.  All rights reserved.

TAPE FAILURE MESSAGE "INTERNAL ERROR 5 RC=17":

The message "internal error 5 rc=17" occurs when any tape other
than tapes designated for 150 MB backups is used.  This message
is saying "the tape you have does not support 150 MB".  The tape
drive recognizes the cartridge and, if it is of a smaller
capacity, reports this fact back to the tape driver.

MTBF AND HEAD LIFE OF 3COM 60 MB and 150 MB TAPE DRIVES:

The MTBF (Mean Time Between Failure) of the Wangtek 60 MB tape
drive is 8,500 hours based on a 15% duty cycle.  The term duty
cycle is defined as the unit being powered up for 8,500 hours
with tape moving across the tape head 15% of the total system
power-on time.  The most common failures are heads or motors,
both of which are used only during tape motion, so the effective
MTBF depends on hours of actual tape motion.

This means an effective MTBF OF ~2000 hours with the newer HWR-
(high wear resistant) style Wangtek heads (or 1275 hours with the
older heads shipped prior to April 1987.)  The HWR-style heads
have been used in all 3Com Wangtek repairs/exchanges since their
availability.

With the Tandberg and Archive drives, the head life generally
exceeds the MTBF of the motor, which is observed to be ~2000
hours.

Typical head life with various types of tapes and drives is shown
in the table below.
                                 Hours of Tape Motion
Brand       Tape           Wangtek Tand/Arch Tandberg Archive
                            60 MB   120 MB   150 MB   150 MB
-----  -----------------   -------  ------   ------   ------
 3M    DC 600 XTD           <2000   ~3500    ~3500    ~3500
 Dysan 612                  <2000   ~3500    ~3500    ~3500
 DEI   Series Gold Plus**   <2000   ~3500    ~3500    ~3500

 3M    DC 600A              <2000   ~3000      N/A     N/A
 DEI   Series II Gold       <2000   ~3000      N/A     N/A

 DEI   600L                  2000     N/A      N/A      N/A
 3M    DC 300 XLP        450'=45 MB   N/A      N/A      N/A

** Currently under evaluation by 3Com.

SPECIFICATIONS FOR TAPE CARTRIDGE LIFE:

The tapes supported for use with 150 MB operation are higher
sensitivity 550 Oersted tape with 12,500 flux transitions per
inch.  550 Oersted tape with 10,000 flux transitions per inch
will support 120 MB tape operation, while 310 Oersted tape is
generally sufficient for 60 MB operation.

All tapes are guaranteed for 5000 passes; however, this is
somewhat misleading as one pass is not necessarily a full backup.
This is because the 600L requires 9 tracks to capture 60 MB, the
DEI Series II Gold and equivalents require 15 tracks to capture
120 MB, and the 3M 600 XTD and equivalents require 18 tracks to
capture 150 MB.

Note also that a pass is not necessarily a motion from one end to
the other, but also describes partial motion, i.e., partial
backups and "shoe-shines", the latter being considered as four
(4) motions.

Excluding retensioning and erasing, this means that the 600L is
guaranteed for 555 backups (5000/9) in a 60 MB drive.  In a 60
MB drive, the Series II Gold is guaranteed for 555 passes as
well.

