WOL: how does it work?

[Robert G. Brown]

On Fri, 7 Sep 2001, Greg Lindahl wrote:

> On Fri, Sep 07, 2001 at 12:20:48PM -0700, Martin Siegert wrote:
>
> > Here is the problem: Each node draws a current of about 1.5A (I measured
> > that a few days ago). Since I have about 70 of those, booting all nodes
> > at once will draw all of the sudden a current of more than 100A. The
> > people who run our machine room don't allow me to do that (probably for
> > good reason).
>
> I can't really answer your question, but there's an alternate
> solution. You can use a device which delays the booting of some
> nodes. For example, the APC MasterSwitch has the ability to let you
> power cycle nodes by attaching to a web browser, but another feature
> is that it can power up the nodes with a delay after a power failure.
> It's a bit expensive for this purpose ($354 for 8 plugs @ 120V, 12A
> total), but maybe you can find something cheaper, such as an X10 based
> controller.

I haven't yet tried it, but a lot of ethernet cards now support Wake On
Lan, and ATX power supplies can boot in software once power is delivered
to the switching supply.  They are usually the better ethernet cards
anyway, the sort one would probably prefer to use in a cluster.

We were hoping/planning to arrange it so that a relative few master
nodes controlled when the slave nodes start up (and shut down in the
event of a loss of AC).  Is this not possible?

   rgb

-- 
Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu