SUMMARY: dump parameters for an 8 mm exabyte tape drive

From: Ian Lumb (
Date: Tue Feb 16 1993 - 03:55:35 CST


I originally asked for the optimum parameters relating to dumps on a 5GB
exabyte tape. Although I received 16 responses, the most comprehensive was
a previous summary forwarded to me by Scott Crosbie
<> that was apparently written originally by Since the info that I received served
mainly to reiterate what Scott sent me, I am taking the liberty of
re-posting the previous summary.


Ian Lumb     Internet: <>
Earth & Atmospheric Science, York University
North York, Ontario  M3J 1P3,  CANADA
Voice: (416) 736-5245; Fax: (416) 736-5817

---------- Forwarded message ---------- Date: Mon, 15 Feb 93 10:28:37 EST From: Scott Crosbie <> To: Subject: Re: dump parameters for an 8 mm exabyte tape drive

We give it the dump 0dsbfu 54000 13000 126 /dev/rst10 /dev/partition

Here's a previous summary from sun-managers

[mail header info deleted]

>From Mon Sep 14 23:45:16 1992 To: From: Subject: Summary : 5 gig Exabyte problems.

Thanks for all of your replies on how to write 5 gigs to a high density exabyte. We now have a machine that works. There were dozens of replies so to summarise I have just picked out the key points.

a) Always use new tapes, especially with earlier releases of SunOS, ie) 4.0.* or 4.1.1. If you use a tape thats been used on a low density drive, you will not be able to write in high density mode to it.

b) If your 5 gig exabyte machine has been writing in 2.4 gig, low density mode, you will need to power cycle it as SUn's driver is flakey about switching density modes.

c) 2 gigs is the file size limit under SUnOS, so consequently that is the maximun amount that a single file can be written to tape.

d) rst[0-7] are for low density and rst[8-15] are for high density.

e) The figures that we now use for a level 0 dump are :

dump 0ubdsf 126 54000 13000 /dev/rst8

However everyone else seemed to have there own. I can't say if they work, but I know ours do for us. Here are a few other alternatives :

dump 0fubsd 126 108000 6000 /dev/nrst9

dump 0ubdsf 126 54000 6000 /dev/rst8

dump 0ubdsf 126 54000 6000 /dev/nrst0

dump 0ubdsf 126 54000 12000 /dev/rst8

dump 0bdfsu 126 54000 /dev/nrst8 226000

dump 0dsbuf 54000 24000 126 /dev/nrst8

dump 0bdfsu 126 54000 14500 /dev/nrst8

At the end of the day, it seems that you should be safe with

b=126 d=54000 f= /dev/rst8 However there is some discrepancy with s the size parameter. This though is only used to estimate the amount of tape required and to shout when it thinks it has run out of tape. To calculate the size, the following equation has been suggested. size = ((512 * bf ) + 1920) * (ts - 2048) / (bf * 10667) where : bf = blocking factor (eg 126) ts = 2.3*G or 5*G (less for shorter or partially filled tapes) eg) for a 5 gig tape size = (512*126 + 1920) * (5*1024*1024 - 2048) / (126 * 10667) = 259039

I'll leave you all to decide what you think is right. I am sticking with 13000 cos it works.

--------End of Summary-------------

Hope this helps

-Scott ,

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