freebsd-ports/misc/buffer/pkg-descr

This is a program designed to speed up writing tapes on remote tape
drives.  Requirements are shared memory and locks which normally
means that these are supported in your kernel.

[for FreeBSD, this means you MUST have a kernel with 
 options SYSVSHM
 compiled in - markm]

Buffer has been tested under SunOS 4.0.*, SunOS 4.1.*, Solarix, HP-UX 7.0,
and Gould UTX 2.1A (sv universe).

The program splits itself into two processes.  The first process reads
(and reblocks) from stdin into a shared memory buffer.  The second
writes from the shared memory buffer to stdout.  Doing it this way
means that the writing side effectly sits in a tight write loop and
doesn't have to wait for input.  Similarly for the input side.  It is
this waiting that slows down other reblocking processes, like dd.

I run an archive and need to write large chunks out to tape regularly
with an ethernet in the way.  Using 'buffer' in a command like:

	tar cvf - stuff | rsh somebox "buffer > /dev/rst8"

is a factor of 5 faster than the best alternative, gnu tar with its
remote tape option:

	tar cvf somebox:/dev/rst8 stuff