On 8/16/2017 7:49 AM, Chris Olson wrote:
Many thanks to those that responded to my original posting with
information about Network UPS Tools and commercial UPS products.
In our planning a path forward to implement UPS-based power fail
protection, we have come across what appears to be an issue with
the state of the CentOS 6 machines being UPS protected. Most of
these machines are desktop/deskside machines that are likely to
be idle during non-work hours. It is also likely that they will
be hibernating or in a power save mode.
In the power save mode, these machines do not respond to keyboard
or mouse activity. They also do not respond to network traffic
such as a ping from other systems on the network. The method we
use to wake them up is a quick push on the power button when the
hibernation state is indicated by the button's yellow LED display.
This state of hibernation leaves us wondering if these systems will
be able to respond to network messages sent by the UPS. We have not
yet made it all the way through the NUT and UPS documentation.
The hibernation answer may very well be therein, but we have not
found it so far. Any help or direction regarding the hibernation
issue as it relates to UPS power fail protection will be appreciated.
in general, there's two power save states, 'Standby' aka 'Sleep', where
the system state is held in RAM, but the CPU and peripherals is shut
down and sleeping, and "Hibernate" where the ram is saved to disk and
the system is completely powered down.
In sleep, if the power is lost, then you'll need to reboot when the
power comes back up. The system is using very little power, so your
UPS should last much longer.
In hibernate, you can restore when the power returns. Hibernate,
however, takes a few more seconds to wakeup, so people often use Sleep
as it wakes up relatively instantly.
In neither of these states will the system be able to listen to ANY
network traffic, as the processor is simply not running. The one
exception is Wake-On-Lan aka WoL. You probably COULD configure a
master always-on NUT box to send WoL to a list of such systems, wait a
suitable amount of time for them to come back to their senses, then send
them Hibernate commands via NUT.
Utilizing WoL requires configuration on the target hardware to recognize
and accept the WoL, this is typically done at the BIOS level, and only
works if the system supports WoL in the first place. WoL commands can
typically only be sent over the same local network segment, as they are
layer 2 packets sent to the MAC address of the target.
--
john r pierce, recycling bits in santa cruz
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