Summary: Dump parameters for 5GB Exabyte

From: SILL D E (
Date: Fri Apr 26 1991 - 07:24:47 CDT

I asked what dump parameters to use with 5GB EXB-8500's.

From: (Daniel Strick)

    double the tape length

From: (Chuck Smoko - E41)

I have been using out 2.3G Exabytes as an infinite byte storage device
because we don't have 2.3G of disk space on any of our machines (yet).
The way I have been handling the dump command is as follows: 1) Set the
tape length really big (99999999, i.e. infinity), 2) a reasonably high
block factor of 100 (512x100 bytes per READ/WRITE), 3) and of course
the device.

 /etc/dump u0sbf 999999 100 /dev/rst0 /dev/[n]r?????

From: hj%idacrd@Princeton.EDU (Harris A. Jaffee)

We bought our Exabyte hardware and software from APUNIX. They strongly
advise using the standard 10k block size (i.e. the default blocking factor,
20), claiming that a larger size would make the drive wait longer for data
from dump, actually making the drive more inefficient. I have reluctantly
accepted this, without feeling that I've heard a proof. With this block
size, or maybe it doesn't matter, the tape length is 145000 feet. When
you put multiple dumps on 1 tape, you have to be careful that they all will
fit. The 145000 should decrease, in some sense, with each dump. We don't
bother to do this. At one time, it was advised to use the "long tape mark"
in case you needed to back up and re-write. Some ways of re-positioning
used to prevent these re-writes. Our backup script can do this, but never
has in real life. (The Exabytes are VERY slow.)


I ended up just doubling the density recommended in the st man page.
Chuck makes a good point about the density/length parameters: as long
as your dumps fit on one tape, it doesn't really matter what numbers
you use, provided dump calculates that it will need no more than one
tape. Harris also points out that with multiple dumps per tape, you
need to make sure there's room for each successive dump, since dump
doesn't/can't keep track of how much is already on the tape.

Dave Sill (	  It will be a great day when our schools have
Martin Marietta Energy Systems    all the money they need and the Air Force
Workstation Support               has to hold a bake sale to buy a new bomber.

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