[rescue] Block size and the single DD

[Sheldon T. Hall]

 Mike Meredith says ...
> > Sheldon T. Hall wrote:
> > > 	rsh $MACHINE xfsdump -l 0 -F - $FS | dd of=$TAPE bs=$BS
> > > 
> > > I run that on the Sun with values like
> > > 
> > > 	MACHINE=blinky	# Indigo2 R4k
> > > 	FS=/dev/root
> > > 	TAPE=/dev/rmt/1cn	# DLT 2000xt on Sun SBUS card
> > > 	BS=1024k
> 
> You might want to reduce the block size to 32Kbytes. The backup script I
> used to use at work used that block size to write to an L280, and I'm
> pretty sure I benchmarked a wide range of block sizes to check the time.

I'm going to look into the optimal BS for the DLT ...
 
> I seem to recall some people have trouble with blocking over rsh, so it
> may be worth trying something like :-
> 
> 	rsh $MACHINE 'xfsdump -l 0 -F - $FS | dd bs=$BS' | dd \
> 		of=$TAPE bs=$BS

... and maybe use ibs= and obs= with dd, to match the "ends" of the pipe.
 
> Don't forget to sprinkle the chicken blood around.

Fortunately, my wife's a chef, so I can get that stuff by the bucketful.
 
-Shel