SUMMARY-8mm dump parms

From: Brian H. Powell (
Date: Fri Sep 28 1990 - 09:24:22 CDT

     I've received about a dozen responses, and the general consensus seems to
be that, since nobody (who responded) has filesystems as big as 2 Gigabytes,
it doesn't matter what you use for the dump parameters, as long as they
indicate the tape can hold at least 2.3G.
     I got varying responses about the blocking factor (20, 56, 64, and 126).
I heard (but have no evidence to support) that the blocking factor doesn't
matter; that the exabyte always uses its own block size, and buffers data
until it gets that much. I also heard that people occasionally have problems
using large block sizes over a network with rdump.
     Some people (with whom I agree) insist that you need to lie to dump
about the tape parameters. My impression about why this is needed is that
dump assumes that the tape density won't exceed (my guess) 64K. So you either
use a real big size parameter, or a combination of a large density and a
large size parameter.
     The responses are below. Thanks to everyone. Have fun.


From: (Leslie Dreyer)
Blocking factor= 126
Density = 54000
Length (in feet) = 6000

From: (Phil Blanchfield DGBT/DIP)
rdump 0usf 120000 tapemaster@marvin:/dev/nrmt0h /dev/roota

From: (Ron Robert Hall)
/etc/dump ${level}uncsdf 346 466033 /dev/nrst1 /dev/xd0a #/

From: Loki Jorgenson Rm421 <loki@Physics.McGill.CA>
dump u0bdsf 56 54000 6000 /dev/nrst0 /dev/rpart# >>&! /usr/adm/backup.log

From: (Matthew S. Granger)
dump 0ubsdf 20 6000 54000 /dev/rst1

From: (Brent Chivers)
/etc/rdump 0bdsfnu 126 54000 6000 hostname:/dev/nrst0 partition

From: (Chuck Smoko - E41)
dump the -s and -d options of 9999999 and 10000. The size params of

From: aptcorp!venus!brian@Central.Sun.COM (Brian Holgate)
dump 0ufs venus:/dev/nrst1 126000 /dev/rxy0a.

From: (Morry Katz)
set dumpflags="ubsdf 56 5190 4100000"

From: "r.d. parachoniak" <>
Here are the parameters we use: density=54000 size=6000.

From: jerry%asc@boulder.Colorado.EDU (Jerry Stachowski)
/etc/rdump 0ucbsf 126 160000 discovery:/dev/nrst1 /dev/rsd1g

From: aldrich@sunrise.Stanford.EDU (Jeff Aldrich)
/etc/rdump 0ufbs sunrise:/dev/nrst1 64 125000 /

From: iotek! (Michael A. Thompson, Iotek Inc)
rdump 0ufbsdc tapehost:/dev/nrst0 100 6000 54000 /dev/rsd0a

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