Path: utzoo!attcan!uunet!mcsun!ukc!dcl-cs!aber-cs!athene!pcg From: pcg@cs.aber.ac.uk (Piercarlo Grandi) Newsgroups: comp.unix.internals Subject: Re: load sharing Message-ID: Date: 9 Feb 91 19:07:43 GMT References: <25860@adm.brl.mil> <8331@castle.ed.ac.uk> Sender: pcg@aber-cs.UUCP Organization: Coleg Prifysgol Cymru Lines: 50 Nntp-Posting-Host: odin In-reply-to: mfg@castle.ed.ac.uk's message of 7 Feb 91 09:20:19 GMT On 6 Feb 91 16:22:07 GMT, pjw@usna.navy.mil, jw@math30, (Peter J. Welcher (math FACULTY)) said: pjw> The question is, is there any easy way to perform load-sharing, pjw> other than by randomly assigning sections or students to hosts ? fwp1@CC.MsState.Edu (Frank Peters) writes: fpw1> I once toyed with an idea to do something like this using DNS but fpw1> never implemented it. On 7 Feb 91 09:20:19 GMT, mfg@castle.ed.ac.uk (M Gordon) said: mfg> I implemented a similar idea for our network of suns. Named has mfg> been altered to recognise "sun3" and "sun4" as special cases and mfg> use RPC to get a hostname from a server. There were several reaons mfg> for doing it this way, rather than having named doing the polling mfg> itself. These are hacks, that may work or something like that. There are actually two load sharing issues; one is directing logins to specific hosts, another is directing commands to specific hosts. The second is more interesting. There are some posted implementations of shells that will probe various compute servers to find the least loaded using rstatd and then call the rexecd daemon to remote execute the comamdn on the least loaded host. One I think was done by George Goble at Purdue; another by somebody at BTL and is posted in comp.sources.unix. A similar tool is extremely easy to write, a couple dozen lines. It is possible to just use these couple dozen lines as a wrapper around most large or frequently executed commands, or actually take a shell source and stick them in in the section that invokes external commands. I think that the heuristic of choosing the lowest load average host is not one of the best, but at least is simple; I think that memory size and whether the host has local or remote access to the files needed by the command should be taken into account. Doing a nice system that will execute each command, maybe described in some profile file, on the most apropriate machine, is a nice research project. Directing logins is an easier exercise; usually, if one has remote command execution as above, a simple rotor (FIFO) style policy will suffice. Many rlogin boxes will do it automatically. -- Piercarlo Grandi | ARPA: pcg%uk.ac.aber.cs@nsfnet-relay.ac.uk Dept of CS, UCW Aberystwyth | UUCP: ...!mcsun!ukc!aber-cs!pcg Penglais, Aberystwyth SY23 3BZ, UK | INET: pcg@cs.aber.ac.uk Brought to you by Super Global Mega Corp .com