I think it’s more the fact that they will be losing power for 8 hours on the A 

But yes, always best practice to have A and B, however, this is not always 
suitable in certain circumstances. For example in one facility we have 
dedicated servers in, we have A only. We know the risks of it as does the 
clients buying those services.

Simon, thanks for the explanation. I guess this is a decision you take as a DC 
operator that is again, not the law, but a OH & S precaution. As none of those 
standards advise that the boards need to be de energised to perform the work.

Both Global Switch and Equinix do this live or without interruption, as both 
sites that I have been in have never had an A or B interruption during annual 


Jared Hirst
Servers Australia Pty Ltd
Phone: +61 2 8115 8801
From: AusNOG <ausnog-boun...@lists.ausnog.net> on behalf of Mark Smith 
Sent: Saturday, August 12, 2017 12:53:41 PM
To: Mark Newton
Cc: <ausnog@lists.ausnog.net>; ausnog-requ...@lists.ausnog.net; 
Subject: Re: [AusNOG] NextDC Melbourne - Scheduled Power Maintenance -, 15th 


At least in this situation you'll likely get advanced notice your power is 
going to go away. When your gear has or sufferers from an unexpected PSU or 
other failure, you don't.

This fundamentally goes to the difference between what availability you happen 
to get verses what availability you design and engineer to be assured to get.

You'll eventually pay the price if you assume coincidental 100% past 
availability guaratees future 100% availability. It's pretending failure never 

If you think you are or would be paying a lot for redundancy, you probably 
haven't calculated the cost of down time of the service (e.g., lost customer 
sales, staff sitting around being paid yet unable to do their jobs). That cost 
of down time is likely to be well in excess of any redundancy costs.

Technical infrastructure redundancy is a form of insurance. Would you go 
without theft, fire and other types of business insurance just because it has 
never happened to you before?

On 11 Aug. 2017 04:54, "Mark Newton" 
<new...@atdot.dotat.org<mailto:new...@atdot.dotat.org>> wrote:
As someone who has run colo facilities before:

It should be made completely clear during customer onboarding that the facility 
operator can temporarily shut down a power feed at any time. Advance warning 
should be desirable but optional.

If there is risk involved in doing that, it’s your job to mitigate it. The 
facility operator doesn’t know which bits of equipment in your tenancy are 
critical, and they’ve already told you to dual-feed where possible and use a 
rack-mount ATS for single-corded equipment.

Power work should be done during business hours, because it’s almost impossible 
to get emergency support or source replacement equipment out of hours.

If it isn’t safe to take a power feed offline during business hours, then you 
(the customer) have a design problem to solve.

  - mark

> On Aug 10, 2017, at 6:56 AM, Nathan Brookfield 
> <nathan.brookfi...@simtronic.com.au<mailto:nathan.brookfi...@simtronic.com.au>>
>  wrote:
> Chad,
> That's all well and good but when you're paying a premium price for services 
> of this fashion you expect a certain level of service.  There is a risk no 
> matter what when switching from power supplies taking extra load they would 
> not usually take as well as swing load issues with PDU's.
> I completely agree with your sentiment but the risk is not to be ignored 
> especially during those times.
> Kindest Regards,
> Nathan Brookfield (VK2NAB)
> -----Original Message-----
> From: AusNOG 
> [mailto:ausnog-boun...@lists.ausnog.net<mailto:ausnog-boun...@lists.ausnog.net>]
>  On Behalf Of Chad Kelly
> Sent: Thursday, August 10, 2017 2:54 PM
> To: ausnog@lists.ausnog.net<mailto:ausnog@lists.ausnog.net>; 
> ausnog-requ...@lists.ausnog.net<mailto:ausnog-requ...@lists.ausnog.net>
> Subject: Re: [AusNOG] NextDC Melbourne - Scheduled Power Maintenance -, 15th 
> August
> On 8/10/2017 10:13 AM, 
> ausnog-requ...@lists.ausnog.net<mailto:ausnog-requ...@lists.ausnog.net> wrote:
>> From the latest update today, It appears that most of the works are
>> being postponed for the time being
>> Not all devices within racks support 2 feeds and planning is involved
>> with these devices, which is why it is crucial to receive accurate 
>> information about any pending outages or upgrades to the NextDC DataCentres 
>> which affect services.
> If these services are mission critical then you really should have duel PSU 
> units, so that when one feed gets taken offline the equipment automatically 
> switches to the other feed. They won't just disconnect both feeds at once 
> because that would be stupid and if the entire DC was offline for too much 
> time then that would put the owners in a rather awkward situation legally, as 
> after say 8 or 10 hours of downtime it wouldn't be good for the owners lets 
> put it that way.
> If the single PSU units are a part of a customers co-located equipment then 
> really your terms of service agreement should exclude liability under your 
> maintenance clauses.
> I don't understand why anyone would be using single PSU equipment in a DC 
> environment now a days when you can buy refurbished servers that come with 
> two PSU as standard even when you buy them without raid.
> Also for anything that is really really mission critical you should have it 
> hosted in multiple datacentres anyway so if something stupid does happen that 
> you can't control you at least still have services online as the load 
> balanced services would just switch.
> Regards Chad.
> --
> Chad Kelly
> Manager
> CPK Web Services
> Phone 03 5273 0246
> Web www.cpkws.com.au<http://www.cpkws.com.au>
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