If you consider saving power in a datacenter, make sure it's a total sollution. So if you can power down several servers, you want the cooling of the hall go down with them. (energy consumption of the cooling system of the hall is a very big chunk of the bill) For several years now, saving energy has been part of the job. However, I had to find out that server hardware is still not ready . We used servers from the three major OEM's we all know and despite what they tell us, 3 out of 10 servers fail before the first year of use. Compared to 1 in 10 when not power cycliing those beasts. We ended up only powering down the development hardware, it was impossible to do for production (availability) and too difficult to predict for staging (long term stability testing of systems and software). The rest of the management supports energy saving, but doesn't take compromises when it comes to availability. There is an advantage in powering down a server regularly. If there is something wrong with the system or the configuration, you will immediately know it. Therefore we power down every server we have approximately every three months. Needless to say that some operating systems also benefit from that action. Where we did a reboot before, we do a powerdown now. So some tips for the brave: First of all, disks do an will fail, invest in spare disks for the systems you want to power down regularly. Make sure you have a monitoring/logging system that warns you in time. Rebuilding a large disk subsystem takes time, so make sure it is finished before the next power down or suffer the consequences. Second, make sure you have a good service contract (comes with most servers) and work on relations with that service provider, they can and will save your job in case of emergency. If they cannot promise greeat service, find another provider, the big OEM's all have a long list of independent providers who are faster and better than the one of the OEM itself. They will honor the support contract of the OEM without extra cost. You will need them for disks, cabinet backplanes, disk controllers and in a rare case, a motherboard. Good luck with your green mean furture! ;-)