That certainly seems logical enough, given the constraints that require Y-cabling. It should give you NSPOF for power.
If the ab/bc/cd/da 4-machine cycle works, great; I suspect it may be easier to hook things up slightly differently, assuming you have enough outlets per rack:
Hook a1 up to its own outlet. Y-cable a2 and b2, b1 and c1, c2 and d2, all the way down. Hook z2 up to its own outlet.
Net requirement: N + 1 outlets for N machines, meaning with 19 outlets you can do 18 machines in a rack. Each machine on a unique pair of outlets for remote power. No stretched Y cables.
(Assuming these are 2U machines and a 40U or so rack, that's pretty close to fully packed, and I'm ignoring space for fans, PDUs, remote power controllers, KVMs, whatever...though some of those would eat up outlets too.)
Just be careful about power phase. It's possible that your two different circuits are on different phases on power. Just be sure your redundant power supplies can actually handle the multi-phase power. It's quite possible that there's no issue at all, but it's also possible that the redundancy makes some assumption on the various HOT leads coming in. YMMV. Just something to think about.
Sounds clever to me, but as cords themselves are also potential points of failure, doubling them up could mean a worst-case scenario of downing three machines by powering off two outlets. Should be ok if the equipment in question reports how many (and even better, which) power supply(ies) it's currently running on so you can check first.
Additional considerationsjlwJanuary 20 2006, 20:27:31 UTC
Sometimes I'll plug one side into the UPS, and the other into utility power. UPSen never, ever fail, do they?
Then there's the layer-2 equipment that has three power supplies, but requires at least two of them energized to get enough to power all the cards in the box. This means you can't do the dual power thing because someday the one that two are on will fail leaving insufficient power. For full redundancy on these you need two separate UPS circuits (or three if you don't use utility power).
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If the ab/bc/cd/da 4-machine cycle works, great; I suspect it may be easier to hook things up slightly differently, assuming you have enough outlets per rack:
Hook a1 up to its own outlet. Y-cable a2 and b2, b1 and c1, c2 and d2, all the way down. Hook z2 up to its own outlet.
Net requirement: N + 1 outlets for N machines, meaning with 19 outlets you can do 18 machines in a rack. Each machine on a unique pair of outlets for remote power. No stretched Y cables.
(Assuming these are 2U machines and a 40U or so rack, that's pretty close to fully packed, and I'm ignoring space for fans, PDUs, remote power controllers, KVMs, whatever...though some of those would eat up outlets too.)
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fail, do they?
Then there's the layer-2 equipment that has three power supplies, but requires at least two of them energized to get enough to power all the cards in the box. This means you can't do the dual power thing because someday the one that two are on will fail leaving insufficient power. For full redundancy on these you need two separate UPS circuits (or three if you don't use utility power).
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