Hi all, Totally agree with all the below, the error was ours originally for accepting their terms at face value. Our interpretation here is that redundant would imply that a single UPS cannot fail and take both feeds offline. While Diverse means two separate UPS systems, fed via two separate ATS panels in different locations, from different mains and generator feeds. The customer must then specify which option they want and accept the difference in cost, just as we did.
So when we originally ordered this location we specifically asked for the power to be diverse from different systems, hence, the separate line item charges. We are, by comparison to them, a small operator in terms of size/scale - they are in the billions globally, so we honestly just presumed that something which is sold using those words (after requesting diversity as we did) would definitely not be just two feeds from the same bar. Lesson very much learnt…!! To be honest, I’ve come to accept that many facilities claim ‘diverse’ as being nothing more than from two separate PDUs upstream, but at least they are usually connected to a UPS chain which can tolerate a failure of a single battery. So even if you look beyond the use of the word ‘diverse’ I really can’t see how it can be considered remotely redundant whatsoever, but hey. Anyway, thanks for the input – I’ll continue my discussions with them…! Cheers, Robert Williams Custodian Data Centres https://www.CustodianDC.com From: John Bourke <[email protected]> Sent: 17 October 2018 11:44 To: Robert Williams <[email protected]> Cc: [email protected] Subject: RE: Power Delivery Definitions Hi, I seem to remember that one tier level provides for diverse paths, and the next level up is about having 2+1 for maintainability, so you can work on one UPS and still have diverse paths during maintenance. But if they have only a single UPS …. Thanks John -----Original Message----- From: uknof <[email protected]> On Behalf Of Paul Civati Sent: 17 October 2018 11:30 To: [email protected] Subject: Re: [uknof] Power Delivery Definitions On 17 Oct 2018, at 11:10 am, Robert Williams <[email protected]<mailto:[email protected]>> wrote: > Thus, the overall claim that our dual feed racks have “Redundant Diverse > Power” is, IMHO, false. Unfortunately as I found out to my own cost, DC providers are vague on these things and get away with it. If you walk into a facility that looks the part, and they talk the talk, you can be fooled into believing things are redundant or even up to spec when they aren't. The simple fact is that you have to get it all nailed down in writing or all the talk of redundancy is finger in the air stuff. Even then, asking for N+1 power feeds, and N+1 UPS, you almost need a schematic of how it’s all connected to be fully aware of the failure modes. Too much of all this stuff is marketing BS in my experience. Finally, a lot of SLAs are so weak that they find ways of getting around them, or even if you make an SLA claim, the payout in no way compensates for the level pain you will incur during down time. -Paul- From: uknof <[email protected]> On Behalf Of Edward Dore Sent: 17 October 2018 11:33 To: Robert Williams <[email protected]>; [email protected] Subject: Re: [uknof] Power Delivery Definitions Hi Robert, I’d expect “diverse” to mean a N+N (or better) infrastructure with fully separate A and B feeds to at least the internal distribution and UPS level, so short of something catastrophic happening you should never lose power on both feeds simultaneously. If they’re delivering you what is effectively a pair of A feeds, then it seems somewhat difficult to justify calling them “diverse” unless they’re talking about physical routing of the cables between your rack(s) and their distribution infrastructure? This would seem somewhat disingenuous to me. That said, I’d want it defined in more detail before signing the contract. Maybe I’m just bitter/paranoid though 😉 On the “redundant” side of things, I can certainly understand that whilst in an ideal world you wouldn’t want a single component to cause a failure on even one of the feeds, electrical safety makes this harder to accomplish – better to lose power than to blow something up or even kill somebody. This is why we have a very strong preference for 2N A+B feeds and dual PSU everything. I’d certainly say that the wording you have is too vague to be useful and needs to be clarified with explicit definitions and preferably a functional schematic or block diagram of how the service is delivered. Edward Dore Freethought Internet
