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 From: uknof <[email protected]> on behalf of Robert Williams <[email protected]> Date: Wednesday, 17 October 2018 at 11:12 To: "[email protected]" <[email protected]> Subject: [uknof] Power Delivery Definitions Hi All, I’m not sure if this is an appropriate forum for such a question, so I’ll take silence as a ‘nope’… At the moment we are having a disagreement with another DC provider regarding their power delivery to our racks we are renting there. This started because a few weeks ago they had a fault which resulted in a complete loss of power to both “A” and “B” feeds to our comms racks for approx. 25 minutes. They have since confirmed that this outage was caused by: “…a single UPS battery failing during a mains failure simulation test, resulting in the shutdown of the UPS.” The power solution we are paying for each rack is defined (in their own words) as being made up of two chargeable elements: 1 x “Single Phase Primary Power” 1 x “Single Phase Redundant Diverse Power” Consequently, I now have two issues with them: “Redundant” – As far as I believe, this implies that a system (such as a UPS chain) will be at least N+1 and therefore can tolerate a single failed component or UPS. It should certainly tolerate a single failed battery within a single UPS within a chain. “Diverse” – My understanding of this is that it should include power from two ‘diverse’ sources. Since both our feeds failed in parallel when this single UPS fault occurred. I therefore argue that their solution is not diverse either. Thus, the overall claim that our dual feed racks have “Redundant Diverse Power” is, IMHO, false. Obviously as a provider ourselves we have our own terms and interpretations of power delivery - but I’m not looking to do an ‘Us vs. Them’ or anything, my own view will be skewed anyway. So I’m asking here as I’m genuinely interested in what other people would expect their level of service to be after purchasing products named exactly as I’ve shown above, from a large multinational provider. (I’m also not interested in naming the provider, that’s not what this is about.) I’ve also been unable to find anything particularly useful online, either in terms of backing up my either my understanding of the definitions being used, or backing up their interpretations. I welcome your thoughts – cheers! Robert Williams Custodian Data Centres https://www.CustodianDC.com
