rdump on DEC/SUN UNIX Systems

[Richard Wood]

Reply-to: richard at vajra.UUCP (Richard Wood)


In article <81522 at felix.UUCP> pjb at tcom.stc.co.uk (Peter J. Bishop) writes:
>
> On one of the Suns and one of the DECs we have 6250 bpi tape drives.
> For this reason our main backups are performed using 'rdump'.
> Unfortunately this seems to run DEADLY SLOW. This makes our backups
> last approx 35 hours. As you can guess, his is impractical.
>
>My questions are,
>
>	a) Does anyone know why rdump is so slow (the machines are connected
>	   by ethernet.
>
>	b) How can I speed it up or,
>
>	c) Are there any alternatives.

I suspect that the server rmt process isn't implemented with N-buffer
IO, and thus isn't keeping the tape in streaming mode.  A streaming tape
in start-stop mode is a painful sight to behold.

Suggestion:  Try 
	dump 0unf - /PARTITION | rsh dd of=/dev/rmt0h
	(add other parameters as required)

In other words, just pipe the data across the net manually.  The "dd"
should be able to keep the tape in streaming mode.

(Actually, we were trying to get rmt to do streaming in v3.0 - I don't
know if it made it.  Which version of each OS are you using?)

-- ----------------------------------------------------------------------------
Does it need saying that I'm not speaking as an official representative of DEC?
===============================================================================
Richard Wood  !  U. S. Worksystems, Palo Alto  !  Digital Equipment Corporation