[iloveponies]

One thing I've found interesting: The decision to have batteries not per server like Google, or per data centre, but per group of racks.

[Swannie]

Pretty standard in telecoms. Never quite understood why Google went per server.

[iloveponies]

Their claims were that the efficiency was that great, and that it's acceptable to pay the extra few dollars in motherboard manufacture to build it in.

[Swannie]

I guess in their instance the lifetime of the server was never likely to be eclipsed by that of the battery. In telco, 15-20yrs of operation is not uncommon, so a single set of replaceable/easily service batteries is important.