On Mon, Oct 23, 2023 at 7:38 AM Babak Pasdar <babak@pasdar.com> wrote:
A few months ago, 165 Halsey took us down for several hours. They claimed that a UPS failed causing this issue. Our natural reaction was that we have A/B redundant power so a failed UPS on the A circuit should not take down the cabinet. Joe the facility manager claimed that industry standard A/B power means two circuits to the same UPS, which makes no sense to me.
If they're being truthful (and many folks are not) then A/B power means that your power is redundant back to at least two different UPSes. The UPSes are maintained at under 40% capacity so that a failure of one doesn't cascade to the other. Ideally these UPSes back to two different generators, also maintained at 40% of capacity. In large, fancy data centers they even get power company feeds from two different substations. Don't just ask the sales droid. When they deliver the rack or the cage, ask the data center manager to show you where your power connections run. If they can't or won't... don't believe them. "Industry standard" A/B power does NOT mean two circuits to the same UPS. That's just extra power, not A/B. Joe lied to you. Incidentally, if you're worried about N+1 redundancy, I assume you're hosted at more than one data center from more than one vendor? Buildings and vendors are single points of failure too. Even when built right, stuff happens. Regards, Bill Herrin -- William Herrin bill@herrin.us https://bill.herrin.us/