NMC-controlled UPS shutdown in a mixed PCNS and non-PCNS environment

[alextee_apc]

This was originally posted on APC forums on 11/11/2014

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Hi there,

Been reading this great forum for over a week already. I've studied almost all the topics regarding NMC and PCNS, also read the article written by Steve Jenkins, viewed the shutdown charts and other documents, but it looks as my case is a bit special after all, so I decided to ask for some help.

To begin, I'll describe my use case first. I have the SUA750I with AP9617 NMC installed and properly configured and functioning. The connected equipment is quite diverse; there are two workstations (Windows and Linux), a Synology NAS, and a SOHO wifi router running some custom wrt rom. These devices aren't operating constantly, and are turned on and off independently on demand, but they are all powered from this very UPS in question!

The main reason for adding the NMC was to create a single command point, which would signal all the hosts in case of power failure, then wait for some time until the hosts shutdown, and finally put UPS to sleep state without waiting for the Low Battery Delay to elapse, as it would happen with the PCNS to initiate the UPS Turn Off process. The reason I want the UPS to early shutdown is to preserve battery life, since another power failure can potentially happen soon after the first one. Also, I just don't need the UPS to run that long.

Now, not all hosts are PCNS clients in my environment. For example, NAS supports only SNMP UPS (uses NUT), while the router and the linux (use APCUPSD) machine read UPS status via pcnet (PCNS protocol), which lacks full protocol functionality. Thus, all the hosts, except Windows machine, rely solely on OB and LB (on-battery, low battery) flags to trigger any action (be it shutdown, drive unmount etc), but they neither understand the PCNS graceful shutdown command, nor they can signal back the UPS to make it turn off. Ideally, I'd like to use the LB flag as the key indicator, that the time for shutdown has come! This way, I can configure LDB on NMC to decide when the shutdown process starts on the hosts, and I don't need to extra mess with configuring other triggering conditions (in respond to the OB flag), since PCNS, NUT and APCUPSD are hard-coded to shutdown the systems as soon as they receive the LB signal. I get perfect shutdown synchronization, even if any host was turned ON after the power has failed.

The question is how to signal UPS to perform an early shutdown, since PCNS are mostly not available to tell him to do so. If I set the LBD large enough, the hosts will shutdown quicker, but the UPS will continue wasting its energy counting down until the shutdown timer, which equals LBD, elapses. I am now contemplating on whether to buy the AP9630 NMC, which, as I learned from neighbor topics, is able to perform Controlled Early Shutdown with sending the graceful shutdown command to all the hosts. I'm not sure this is what I exactly need, because graceful shutdown will not be understood by the non-PCNS clients. Is there a way to configure the AP9630 to always set the LB flag whenever the CES meets any of the condition configured? Or, the only way to get the LB flag is when the LBD condition occurs? Then, maybe, using the CES condition of matching the remaining runtime (which should be set to a smaller value than the LBD), will shutdown the UPS after the LBD condition occurred, thus, the hosts must've been shut down already. Am I moving in the correct direction? Could you please share your thoughts and recommendations?

P.S. Is Controlled Early Shutdown on NMC2 supported on SUA750I?

Thanks!

[voidstar_apc · Accepted solution]

This was originally posted on APC forums on 11/11/2014

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Controlled Early Shutdown, aka Load Shedding, should work on a SUA750I with an NMC2. Another option with the latest firmware on NMC1 if you're okay with shutting down after a certain amount of time on battery is to set the OnBatteryShutdownDelay in config.ini. I've attached such a config.ini file.