Re:Proposed server purchase for GitLab.com
by btgeekboy on Sunday December 11, 2016 @08:18PM
(#13154755)
This is good advice. I'd consider not having them auto power on, however. This allows them to bring things up in a controlled manner.
That brings me to my next point: GitLab should also being mindful on what services are stored on which hardware - performing heroics to work around circular dependencies is the last thing you want to be doing when recovering from a power outage.
Re:Proposed server purchase for GitLab.com
by walrus01 on Sunday December 11, 2016 @08:21PM
(#13154775)
Yes, this is a choice that depends on the facility, and what sort of recovery plan you have for total power failure. In many cases you would want to have everything remain off, and have a remote hands person power up certain Network equipment, and key service, before everything else. On the other hand, you may want to design everything to recover itself, without any button pushing from humans.
Depends a lot of server/HA/software architecture.
Build one node with the hardware configuration you intend to use. Same CPU, ram, storage.
Put it on a watt meter accurate to 1W.
Install Debian amd64 on it in a basic config and run 256 threads of the 'cpuburn' package while simultaneously running iozone disk bench and memory benchmarks.
This will give the figure of the absolute maximum load of the server, in watts, when it is running at 100% load on all cores, memory IO, and disk IO.
Watts = heat, since all electricity consumed in a data center is either being used to do physical work like spinning a fan, or is going to end up in the air as heat. Laws of physics. As whatever data center you're using will be responsible for cooling, this is not exactly your problem, but you should be aware of it if you're going to try to do something like 12 kilowatts density per rack.
Then multiply wattage of your prototype unit by number of servers. This will tell you how many fully loaded systems will fit in one 208v 30a circuit on the AC side.
Also, use the system bios option for power recovery to stagger bootup times by 10 seconds each per server, so that in the event of a total power loss and an entire rack of servers does not attempt to power up simultaneously.