[AusNOG] Question about hardware spec for a DC

[Paul Gear]

In my judgement, the big benefit of dual power supplies (particularly on 
servers, switches, & routers) is that it enables reorganising of power 
circuits in racks without requiring a downtime window.  Like you say, a 
comprehensive view of high availability means designing N + 1 redundancy 
at the system level, but dual power supplies to those N + 1 devices is a 
big convenience factor.

Paul

On 04/24/2014 11:25 AM, Colin Stubbs wrote:
> IMHO
>
> Avoid that auto power-transfer stuff in rack if you can. Those devices 
> are best used only for low end boxes like NTU's/etc with which you can 
> only ever install/utilise a single box at a time.
>
> Buy equipment which has dual PSU's as an option in preference, but 
> don't mandate it or mandate buying the two power supplies. Mandating 
> it will just mean you're wasting part of your budget unnecessarily on 
> every single purchase as you may force yourself to buy bigger boxes 
> than required; and/or buy more PSU's than you need.
>
> Avoid *depending* on dual PSU's if you can, e.g. don't design anything 
> with the assumption having two power supplies in a box will keep 
> everything working if there is a loss of power or if one of the PSU's 
> fails.
>
> Design for failure with N+1 redundancy at a system level, e.g. install 
> two or more of every box and use them in active/active or 
> active/standby capacities. If you do that you won't necessarily 
> require two power supplies in each to achieve a very high level of 
> availability.
>
> Choose to use dual PSU's primarily based on the location and the power 
> infrastructure available, in combination with how many boxes you have. 
> e.g. if you're in a crappy DC where they can't deliver access to two 
> genuinely independent sources of power the value of having two PSU's 
> is greatly reduced regardless of how many many boxes you've installed.
>
> Read up on HA concepts if you're not sure what you need or why.
>
> 13 years old now but this book is still handy and the concepts still 
> hold true,
>
> http://www.ciscopress.com/store/high-availability-network-fundamentals-9781587130175
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ausnog.net/pipermail/ausnog/attachments/20140424/126d95e6/attachment.html>