translation of the main points (of the linked article, not the full 43-pages BEA-RI report) :

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.

If the batteries are needed, the power is first converted back into AC before hitting the servers, which will convert it back to DC.

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.