Desc: Typical setups for big servers File: big-servers.txt Date: 30 April 2003 Auth: Russell Kroll <rkroll@exploits.org> By using multiple MONITOR statements in upsmon.conf, you can configure an environment where a large machine with redundant power monitors multiple separate UPSes. For the examples in this document, I will use a HP NetServer LH4 in the stock configuration with 3 out of 4 power supplies installed. The HP is unusual (compared to some systems, at least) in that it has common power plugs for a given side of the server. One plug drives two power supplies. This means that losing one UPS shuts down both of them. Here's the arrangement for our example: UPS "Alpha" is running the plug with two supplies in it. UPS "Beta" is running the other plug, with the single supply. Since the server needs two supplies to stay alive, we can lose "Beta" at any time, but losing "Alpha" is a showstopper. We make a note of them when configuring upsmon: MONITOR ups-alpha@myhost 2 monuser mypass master MONITOR ups-beta@myhost 1 monuser mypass master MINSUPPLIES 2 With that configuration, upsmon will only shut down when Alpha reaches a critical (on battery + low battery) condition, since Beta by itself is not enough to keep the system running. Beta, on the other hand, can go up and down as much as it wants and nothing will happen as long as the other one keeps working. The MINSUPPLIES line tells upsmon that we need at least 2 power supplies to be receiving power from a good UPS (on line or on battery, just not on battery and low battery). Adding redundancy ================= In this case, the server is in the stock setup as received from HP, which has 3 out of 4 installed. Let's say some extra money is found in the budget and we get a fourth supply and install it. The upsmon.conf must now be edited to reflect this: MONITOR ups-alpha@myhost 2 monuser mypass master MONITOR ups-beta@myhost 2 monuser mypass master MINSUPPLIES 2 Beta is now driving two power supplies, so we upgrade its power value. This means that either Alpha *or* Beta can totally shut down and the server will be able to keep running. As an added bonus, this means you can move a running server from one UPS to another without bringing it down since the minimum power will be provided at all times. Other configurations ==================== There are a lot of ways to handle this and they all come down to how many power supplies, power cords and independent UPS connections you have. A system with a 1:1 cord:supply ratio has more wires stuffed behind it, but it's much easier to move things around since any given UPS drives a smaller percentage of the overall power.
