My apologies if this question is silly or vague but I just got around to investigating the UPS settings on a couple of servers I inherited recently, the shutdown timeout on some of these servers is set to 5 minutes, on others it is set as high as 10. I think 10 minutes is wildly optimistic and I am not sure about 5 either. Does anyone know of a, "typical," number of minutes that these are usually set to? These are rack mountable, slightly smaller than an R-Class box. Also, and this would be a great help, does anyone know where I can get some documentation for these? Any help would be appreciated. Thanks in advance.
Sorry, you get a "it depends" answer. What's the size of the UPS? What's the load on it? The only reliable way is to test it and find out how long you can depend on the UPS to keep the system up. Other than doing that, it's an (un)educated guess.
We have shutdown timeout set to 15 mins. Never really tested how long it would stay on UPS though. If the power#s not coming back we try to shutdown ASAP.
You didn't mention what software you are using in conjunction with your UPS, but I believe if you are using ups_mond(1M) that the sum of 'shutdown_delay_minutes' and 'shutdown_timeout_minutes' cannot exceed 15.
There is an element of experimentation when setting these parameters - you should time how long your machine takes to run a shutdown and add a safety margin for 'shutdown_timeout_minutes'. The other parameter should be based on the quality of the mains supply at your site - if there is a chance of an occasional dropout which lasts for 2 minutes then 'shutdown_delay_minutes' should be greater than 2 minutes, else the server will shutdown every time you have one of these dropouts.
