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. 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 -o /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 We have been using buffer here at Imperial for a couple of years now for writing tar tapes and the main system dumps. Thanks to Kevin Twidle <kpt@doc.ic.ac.uk> for the -p and -B code. Thanks to Bard Isley <brad@slammer.atl.ga.us> for fixes to the read loop/SIGCHLD handling. Thanks to PerSteinar.Iversen@fi.uib.no for the DEC Alpha patches. Thanks to kargard@ampex.com (Erik L. Kargard) for the AMPEX enhancements. INSTALLATION: Check that your kernel supports shared memory and semaphores. A quick way to check is to build buffer and run it. If it says "couldn't create shared memory segment" you probably need to reconfigure and rebuild your kernel. To install edit the Makefile and tailor the variables to your local systems. Then type make. DISCLAIMER: This package is under the GNU GENERAL PUBLIC LICENSE! In addtion under NO circumstances can I, or Imperial College, be held liable for any event caused by the running or storing of this program or its documentation. Lee McLoughlin. Phone: +44 171 594 8388 IC-Parc, William Penney Lab, Fax: +44 171 594 8449 Imperial College, London, SW7 2BZ, UK Email: L.McLoughlin@doc.ic.ac.uk
