[AusNOG] Primus Outage explanation

[Paul Brooks]

Without wanting to dampen the flame party, I'll point out that its 
(only!) the people on 240VAC distribution that have problems - the 
carriers that I know were plugged into the -48VDC  supply were 
unaffected this time, and last time also experienced no pain at all.

Yes, the substation has been a bit flaky - but substations do that, 
which is why we assume they will fail and build in backup power 
arrangements for that contingency.
Yes, the gensets have been flaky when they've been called on - but 
gensets are Murphy's favourites, and they do that, no matter how many 
times they are diligently tested.
Its the backup batteries that bridge the gap between mains power failing 
and genset starting that are the real key - and in Primus's case, the 
last failure showed the -48VDC supply has the telco-grade 6 - 8 hours or 
more of reserve capacity, while the 240VAC UPS seems to have only about 
30 minutes of battery. This is the *real* root cause IMHO.

Personally, I try to have at least 4 hours of battery life available - 
which is generally enough time for the gensets to fail to start, get an 
engineer on-site to attempt a manual start, and then kick/swear/curse 
and threaten with escalating sizes of spanners until the genset kicks 
over, or the mains power reappears, whichever comes first.

-- 
Paul Brooks               |         Mob +61 414 366 605
Layer 10 Advisory         |         Ph  +61 2 9402 7355
-------------------------------------------------------
Layer 10 - telecommunications strategy & network design