APC PDU Pair Load Monitoring

Assumes that the PDU is dual bank, i.e. an APC PDU which has a 16A or 32A input, which is then split into two 8A or two 16A banks. The script takes two inputs for the PDUs to monitor. It compares the Bank 1 of the first PDU with Bank 1 of second PDU, it then compares Bank 2 load of the first PDU with Bank 2 load of the second PDU. The script has the purpose of dealing with situation where you have equipment that is dual powered from two PDUs.

For example a switch with two PSUs, one PSU is powered from PDU 1 (A) and the second PSU is powered from PDU 2 (B), it is assumed they are connected to the same outlet in the same Bank on the A and B side PDU. Now assume all equipment is connected up in this same way.

In normal operation you are fine, power can be drawn from PDU A and PDU B, but if you have overcommitted one or both banks, then if a PDU feed was to be lost then the full load would need to be provided by the surviving PDU (and feed) which could be a problem.

For example if you are running at PDU 1 (A) Bank 1 at 12Amps, and PDU 2 (B) Bank 1 at 12 Amps, but the Bank can only deliver 16Amps then in a failure scenario the surviving bank would likely trip out causing a complete outage. The script therefore collects power load information from both PDUs and combines them to look for an issue. PDU 1 (A) Bank 1 drawing 12 Amps isn't a problem if PDU 2 (B) Bank 1 is only drawing 2 Amps, but it is a problem if PDU 2 (B) Bank 1 is also drawing 12 Amps.

Example Usage
./check_apc_pdu_1ph.sh pduA.domain.com pduB.domain.com public 14.0

The example above checks the two PDUs combines the load of bank 1 of PDU A with load of bank 1 of PDU B, if this is over the threshold you have input as the issue threshold then it returns critical otherwise it returns OK. So in this example bank 1 on each PDU can provide a maximum of 16Amps therefore load on Bank 1 of PDU A and Bank 2 of PDU B should not exceed a combined total of 14 Amps to still provide power (without trip) in the event of a PDU or supply failure.

Limitations
Only works on a single Phase APC PDU with 2 banks.