Re: freebsd-questions Digest, Vol 196, Issue 38

On Fri, 09 Nov 2007 16:33:34 +0000 Christopher Key <cjk32@xxxxxxxxx>
wrote:

Apolgies for the slightly OT post, but I'm hoping that some of the
ammased expertise might be able to suggest a solution.

I've a FreeBSD fileserver, a solid state router (Linksys box running
OpenWRT) and a couple of gigabit switches that I'd like to move onto a
UPS (I'm primarily looking at the APC Smart-UPS line).

The requirements for the FreeBSD system are pretty simple, it's not
likely to be of any use if the power's out, so after a few minutes to
allow any files open over the network to be saved, it should perform an
orderly shutdown and remain off until the power returns. However, the
router is a little different. It maintains some state information in
RAM (dhcp leases etc) that I'd prefer not to lose during a short power
outage, and it would also be useful to retain internet access, so
ideally I'd like the router and switches to stay up for as long as the
battery lasts in the UPS.

Space and budget are limited, so ideally I'd like to achieve all this
with a single UPS, which is where the problems arise. As I understant
it, when the UPS wants to wake the attached machines up, it power cycles
its output. This however will reset the router, which was what I was
hoping to avoid.


I've thought around the problem for some time, but not come up with any
convincing solutions:

1) Use some sort of WOL command from the router to the FreeBSD system
rather than having the UPS power cycle its output. How does the router
know the power's returned? Can the UPS be set not to power cycle its
power output when the power returns?

2) Use a second cheap UPS to 'protect' the router whilst the primary UPS
cycles its power output. This seems rather crude, and would presumably
reduce the battery life of the primary UPS due the losses in the second UPS.

By the above, I understand you to be proposing to plug the "secondary"
into the "primary", rather than powering the two UPSes separately. Why
would you do the former rather than the latter?

3) Have the UPS wake the PC via some other means. USB would seem to
ideal choice, but the motherboard won't do a wake on USB from S5, and
I'm can't find a UPS with an ethernet interface.

4) KISS. Buy two smaller, cheapers UPS units.

I think that 4) may be the answer, though with this modification: buy
the heavy duty UPS based on the server's needs. The router draws almost no
current, probably far less than the UPS itself does when the line power has
failed. Buy a minimal capacity UPS for the router, switches, etc. It will
probably be able to keep them running for many hours, likely even days,
during a power failure. Plug it into its own line current socket, not into
the other UPS.


Scott Bennett, Comm. ASMELG, CFIAG
**********************************************************************
* Internet: bennett at cs.niu.edu *
*--------------------------------------------------------------------*
* "A well regulated and disciplined militia, is at all times a good *
* objection to the introduction of that bane of all free governments *
* -- a standing army." *
* -- Gov. John Han***, New York Journal, 28 January 1790 *
**********************************************************************
_______________________________________________
freebsd-questions@xxxxxxxxxxx mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-questions
To unsubscribe, send any mail to "freebsd-questions-unsubscribe@xxxxxxxxxxx"