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 From: Robert Williams <[email protected]> Sent: 17 October 2018 11:38 To: John Bourke <[email protected]> Cc: [email protected] Subject: RE: Power Delivery Definitions Hi John, Thanks very much for that, I'm semi-familiar with the Tier system but unfortunately it also doesn't specifically define such terms either. Whilst it defines relatively clearly the concepts against which the facility should operate with terms such as Concurrent Maintainability and so forth - it doesn't actually have any specifics regarding the power delivery options to the consumers - nor what they should be called (unless I'm missing it). My understanding is a facility could be Tier 2 or 3 and deliver you power from two separate UPS chains (to achieve diversity and redundancy) but a different facility could be Tier 4 with multiple N+1 chains and chose to give you two feeds from the same chain. Which would be worse, but technically would not stop the facility itself from being classified as Tier 4. If anything, I'm feeling more 'mislead' by their use of terms (and charges). We've been paying for protection against exactly this - a single failure in a single component - and in essence, we have been given little more than a single feed with a splitter on the end of it. I guess what I'm ultimately trying to ask is, if you were to purchase racks with "Redundant Diverse Power Feeds", what would you expect the level of service to be? Cheers, [Custodian Data Centres]<https://www.custodiandc.com> Robert Williams Technical Director [Email] [email protected]<mailto:[email protected]> [Call] +44 (0)1622 230382 Review us on Google - your feedback is invaluable to us!<https://goo.gl/trEs7h> Registered Office: Vinters Business Park, New Cut Rd, Maidstone, Kent ME14 5NZ Company Number 07878023 Click here to view our email disclaimer<https://www.custodiandc.com/email-disclaimer> From: John Bourke <[email protected]<mailto:[email protected]>> Sent: 17 October 2018 11:17 To: Robert Williams <[email protected]<mailto:[email protected]>>; [email protected]<mailto:[email protected]> Subject: RE: Power Delivery Definitions Hi, Here is the starting point for the system used to define redundancy at data centres. There is a Tier system which defines various levels of redundancy and maintainability. https://en.wikipedia.org/wiki/Uptime_Institute The conversation with the DC could be "what Tier level do you provide". If they cannot answer that, they are not a serious DC Thanks John From: uknof <[email protected]<mailto:[email protected]>> On Behalf Of Robert Williams Sent: 17 October 2018 11:10 To: [email protected]<mailto:[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
