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molyss | 3 years ago
Fire started simultaneously in a battery and and in a power inverter. It doesn't look like there's any comment on why/how it started on either and how/why it started on both at the same time.
Batteries were lead-acid, not Lithium-Ion (lead-acid is supposed to be less of a fire-hazard).
There's timestamped video of the start of the fire. Alarm was triggered within less than a minute. Someone was at the initial fire location within 2 minutes. Building was evacuated within 4 minutes. Fire Department called within 7 minutes of fire start. On site 17 minutes later. Power company is called within 17 minutes of the 1st fire alarm. Power company couldn't cut power from the substation because of fire risk (and delay to get approval from OVH, which owned the substation). The upstream substation is shut down 80minutes after the fire started.
The fire-engulfed building still has power for another 98 minutes. Fire is considered under control 3h after that (6h after it started), extinguished another 3h later.
There was significant concern that the building would collapse.
There was no fire sprinklers or fire-extinguishing mechanism in the building itself. Water supply was insufficient (single fire hydrant delivering 16k gallons/h). Now water reserve, or pumping mechanism (the Rhein was super close).
Only after 2h were the firefighter able to throw water at the blaze. Before that, there was still electrical power on site.
Recommendations:
Battery storage already have some regulation WRT fire hazard. Charging equipment don't. Apply the same rules for both
improve the ability to cut power from a site
There's a bunch of question that pop in my mind :
Concerning the construction, how common is it to have a 1-h fire resistance ? In the report, they say the floors are made out of wood with a treatment to allow for 1h firewall, and the "internal structure" has a 1h "fire stability". That sounds awfully low to me, especially considering that the fire took 6h to control, 10h to clear.
What's "R-5" concrete structure ?
The power is provided through 2 redundant 20kV AC lines. Then, the power can follow one of 3 path :
directly fed into the hardware if it's "clean" enough
corrected to be cleaner before being fed into the hardware.
converted to DC before being fed into the batteries.
My question : Why don't we convert all the power to DC in a central location before feeding DC power to the servers ? I would expect some significant saving costs in DC->AC conversion, no need for AC "cleaning", and the ability to extract the AC->DC conversion out of the servers (increasing density, and removing some more heat close to the servers). I'm sure it's not a new "idea", I'm just curious as to why it's not a good one.
On the report itself, it looks like the presence of battery makes electrical cutoff much harder. If you cut the main power lines, the batteries and power generators take over, so your DC is still powered.
wongarsu|3 years ago
The DC consumed by the server is 12V. AC is 240V (in Europe). That means you need about 20 times thicker wires to carry the same current. And running 240V DC doesn't win you anything because converting that to 12V DC is more trouble than converting 240V AC to 12V DC.
That doesn't mean it never happens, but it's more typical where distances are short. The network equipment you ISP has in a box somewhere on your street is often feed through AC for normal operation, but connected to the battery backup via a DC line. There cable runs are short and low-ish current, and the efficiency gain from not doing DC->AC->DC matters
walrus01|3 years ago
individual servers then have 48vdc-to-12vdc high efficiency power supplies to create power usable by their motherboards.
of course you don't want to run cables for 12vdc around anywhere.
https://www.google.com/search?client=firefox-b-d&q=open+comp...
garaetjjte|3 years ago
It is true that it doesn't win you anything, but it's not more difficult. In fact you can connect DC voltage to ordinary switching power supply just fine.
toast0|3 years ago
Fire rating requirements are for human safety and not really property safety. In this case, 1 hour rating was more than sufficient for everyone to exit.
The type of use/occupancy of the building generally sets the requirements; I don't know requirements for data centers. 1 hour is kind of the start of enhanced fire ratings; some things might not have a requirement of even 1 hour, others may have more. A large enough fire rating (again, depending on use), may be considered a firewall which can be used to consider each side a seperate building for fire planning purposes. A smaller, but still large rating may be needed to partition spaces with different needs. Higher ratings are common for stairwells, and I wouldn't be surprised if they were required for the battery room and other areas of concentrated risk.
> Why don't we convert all the power to DC in a central location before feeding DC power to the servers ?
Some datacenters do run servers on DC, typically phone companies, and typically -48VDC. This has pros and cons. You may simplify power conversion from batteries, and the ac -> dc input step will likely clean the power, too. But 48v is much lower than common AC voltages, and lower voltage means more current for the same power, which means more loss in transmission and larger conductors required and more heat generated as well.
You still need individual power supplies on each computer, as you need to go from -48v to +12v (and maybe some others, depending). Historically, DC/DC voltage conversion was much less efficient than AC/DC, but that's less true today.
Well designed AC switching can happen at the zero crossing, which can reduce arcing, which is sometimes useful.
unknown|3 years ago
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