[K12OSN] Re: Tossing around an idea...need some input (Jim McQuillan)

Matt Oquist moquist at majen.net
Mon Aug 15 16:59:26 UTC 2005


> Date: Sat, 13 Aug 2005 10:06:11 -0400 (EDT)
> From: Jim McQuillan <jam at mcquil.com>
> Subject: Re: [K12OSN] Re: Tossing around an idea...need some input

> the 'next-server' parameter is used by the bootrom.  I know that
> Etherboot isn't going to work with a hostname, because there is no
> resolver in the Etherboot code.  It's only going to want an IP address.
> 
> I don't know if PXE has a resolver or not, so some experimenting is in
> order.
> 
> the 'root-path' parameter is used by the LTSP initrd image. Again, a
> hostname isn't going to work here, because the initrd doesn't have the
> resolver libraries.  It's expecting a hostname and a directory pathname,
> separated by a colon.

That's interesting; I set hostnames in my dhcpd.conf and restarted the
service, so I'm not sure how it worked...anyhow, it looks like this
discussion is progressing apace (I only get the digest, so I'm usually
late in responding).

Another thought I had was to implement a rudimentary
resources-monitoring system that would rewrite dhcpd.conf and restart
dhcpd accordingly as server loads shift.  For example, if ServerA has
been running at an average of 90% CPU usage for past 5 minutes and
ServerB has been running at an average of 50% CPU usage, write out
a new dhcpd.conf with next-server and root pointing to ServerB and
restart the service.  Keep more stats and check again in 5 minutes,
etc.  It's rudimentary, but it would actually be performing real
boot-time load balancing for the thin-clients rather than splitting
the thin-clients ahead of time to run on one server or another.

Now that I think about it, the policies of the system I've described
probably wouldn't work very well, because everybody in class would
come in and start their clients at once and one server would get the
whole load within in one 5-minute window, and no clients would get
switched to the other server until they reboot...boot-time load
balancing itself is just insufficient.  We won't have real
load-balancing until processes can move between servers...

Dave's hard-coded solution of using the MAC address to put 1/2 of the
clients on one server and 1/2 on the other would do a better job of
balancing everything; it's just more data-processing work for the
admin to manage the MAC addresses.  :)

I don't know if that brain-dump will be useful for anyone, but there
it is anyway.

--matt

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