Most of my datacenter managers are in a locked room with a window into the actual computers. We have been keeping that room dark. My users said it was easier for them to see into the room that holds the servers. There is a big window in that room's wall.
Originally it was to keep the heat down as well. Is it still necessary to do this with modern servers?
This is always an interesting topic to discuss about how to bring down cost of operating datacenter. When we discuss cost, cooling, power, space are key components of any datacenter. No doubt modern servers are more power efficient but they are efficient on space too. Now most of servers come in 1U or 2U size which enables you to have more number of servers per rack. Eventually you draw same or more power per rack. Which leads to more cooling needs. Good thing about "all lights out datacenter" is there no or less human interaction inside the DC, this also adds few pennies to your cooling need.
To bring down cost of cooling, it is always recommended to use less or no lights, use motion sensor lights. To add some extra dollars to your saving keep inventory of datacenter updated, so that you don't have any unused server using your expensive power.
I would recommend you to use LED lights in datacenter in case you want some lights to be kept on for user experience.
I like the idea of the motion sensor lights. We know for a fact that the all lights out policy is saving us money as we did an experiment last year. For one month we kept all the regular lights on, in both the main datacenter and the part of the datacenter where the employees actually have their desks. Our cooling equipment definitely had to work more and it used more energy. Also our lighting costs were more as well. So we will keep to our 'all lights out' policy for now. I like your suggestion of motion sensor lights, as some of the female staff, who work nights, feel a little insecure if there isn't any light. It would be nice for them if they could have some light when they get up to enter the server room, or leave/enter the datacenter itself.
We have definitely found that having the lights off in our datacenter we are saving quite a bit of energy. It also saves us on air conditioning as the rooms do not heat up quite so much. We are slowly reworking our datacenter at the moment and the policy of lights out, is being built into our new energy efficient model.
All lights off in our Datacenter.
