On Nov 4, 2009, at 2:08 PM, Raphael Carrier wrote:
I know you have a rather higher faith in batteries than some of us, but practical experience suggests that batteries are merely a mostly- reliable technology.
Agreed batteries are unreliable, an alternative to battery based UPS are flywheel energy storage devices, they come either as an integrated solution with the diesel generator (i think cat offers such a package) or as a standalone UPS (see: www.pentadyne.com/uploads/18/File/Pentadyne-VSS-Brochure.pdf)
Apparently you do not remember 365 Main... Batteries are reliable. Flywheels are reliable. Both require proper maintenance and proper procedures to handle corner cases (like the multiple-outage corner-case that took out 365 main). Both have their issues. In my experience working at and with a variety of datacenters, I have to day that I have had generally better luck with batteries than flywheels, but, the key difference that suggests flywheels could actually be better technology is this: About 50% of battery failures traced back to human factors. 100% of the flywheel failures I experienced were human factors related. Owen Speaking as an individual, not representing any affiliation.