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Re:Proposed server purchase for GitLab.com by late2part on Sunday December 11, 2016 @08:01PM (#13154661)
note that you can get around the 80% breaker limit by having your DC hardwire the power, if you have enough scale to have them do this for you.
Re:Proposed server purchase for GitLab.com by DanielDent on Sunday December 11, 2016 @09:53PM (#13155141)
Circuit breakers aren't just there for the amusement value of watching a clustered system go into split-brain mode...

I.e. you would also want to be sure that your wiring was rated for 100% utilization, and that other circuit-breaker-like functions exist.

Fire is an actual thing, and figuring out the best way to recharge a halon system isn't exactly what you want to be doing.

Re:Proposed server purchase for GitLab.com by late2part on Sunday December 11, 2016 @11:11PM (#13155476)
Yes. That's why they hardwire and use a breaker rated at 100%. In most jurisdiction, code requires breaker at 80% if a plug/receptacle is used. If you are hardwired you can use 100% of your capacity before tripping the breaker. You have incorrectly assumed that I suggested that you ignore breakers.

When you hardwire the circuit the electrical code allows you to use a 100% breaker.

Re:Proposed server purchase for GitLab.com by DanielDent on Monday December 12, 2016 @12:22AM (#13155764)
Thank you for adding this detail... what you said makes WAY more sense to me now.
Re:Proposed server purchase for GitLab.com by Dylan16807 on Monday December 12, 2016 @03:19AM (#13156502)
What exactly gets hardwired to what? This is surprisingly hard to search for details on.
Re:Proposed server purchase for GitLab.com by late2part on Monday December 12, 2016 @06:33AM (#13157318)
Instead of your plug of your PDU going into a receptacle, the wires that would go into the plug are hardwired to a panel circuit breaker.

This is less common in DCs historically but more and more as folks do 208v 3phase 100A circuits.

Re:Proposed server purchase for GitLab.com by mohctp on Sunday December 11, 2016 @10:03PM (#13155178)
This really is only a concern when you are paying a monthly recurring charge (MRC) by the breaker amp with many power drops.

For a deployment of this scale it should be metered power (For example 1 (or more) 3phase a+b drops to each cabinet) where you only pay a Non-Recurring setup Charge (NRC) and then the MRC is based on actual power draw.

3phase also means fewer physical PDU's (uses less space), but more physical breakers. Over-building delivery capability will eliminate any over-draw concerns for startup cycles.

Re:Proposed server purchase for GitLab.com by late2part on Sunday December 11, 2016 @11:14PM (#13155487)
Not really, although I agree with your reasoning. The other is issue is capex. When I deploy 240kW pods, if I use 80% breakers, I have to deploy 25% more PDUs than if I have 100% breakers.

Since my cabinet number is usually evenly divisible by N*PDUs, this impacts overall capital.

Re:Proposed server purchase for GitLab.com by mohctp on Monday December 12, 2016 @09:29AM (#13158197)
We are talking about 1 to 2 cab density here so capex doesn't carry that much weight.

Having a little headroom on your power circuits is also incredibility important, and not every facility will sell 100% rated breakers. It may make more sense to be in a facility with 80% rated breakers than 100%, even with the added capex of an extra PDU or two.

Goes back to my previous comment. What is important to you, at the pod / multiple pod level, isn't as important to the 1-2 cab deployment.

Re:Proposed server purchase for GitLab.com by late2part on Monday December 12, 2016 @10:08AM (#13158523)
That's fair and accurate.

Similarly, ensure spare room in the cabinet for adjustments, that thing you forgot, and small growth. Much better to have 70% full and not need the space then to have no free RU and need the space.

Re:Proposed server purchase for GitLab.com by late2part on Monday December 12, 2016 @06:35AM (#13157335)
Most DC PDUs will stagger your outlet power on to stagger the initially large power draws.
Re:Proposed server purchase for GitLab.com by mohctp on Monday December 12, 2016 @06:01PM (#13162878)
Some DCs provide PDU's and some don't.