Two Yandex Data Centres in Two Days: What the Sasovo and Kaluga Strikes Took Offline

The number in dispute after Yandex's second data centre was hit in two days is how much capacity is actually gone, and Yandex has not said. On Thursday, Oct. 8, Reuters reported that drones struck the company's Sasovo hub in Russia's Ryazan region, starting a fire and forcing it to suspend operations. On Friday, Oct. 9, Yandex said several modules at its Kaluga region data centre were "completely disabled," according to a second Reuters report.

What the company has disclosed is a verb, not a denominator. It has not published a megawatt figure, a server count or a restoration date for either site.

What Reuters and Yandex have confirmed

Reuters called the Sasovo strike the first major attack on a Russian data hub since the war with Ukraine began. Yandex said Sasovo is one of its five large data centres and that its core consumer services were not affected. On the Yandex Cloud website, the company reported electricity supply problems in one data centre zone and told customers to use others.

Reuters said the Sasovo site hosts tens of thousands of servers. United24 Media gives the site a capacity of up to 12 MW. That figure appears in a background link on a single outlet's page, so treat it as the nameplate design number rather than load at the time of the strike.

The two sites are not equivalent. Kaluga lost modules; Sasovo lost operations.

Site	Date hit	What Yandex said
Sasovo, Ryazan region	Oct. 8	Fire, operations suspended, restoring services
Kaluga region	Oct. 9	Several modules "completely disabled"
Mytishchi, Vladimir	None reported	Blurred on Yandex Maps, per Verstka

The supercomputer question

The detail with the longest tail is the compute. Reuters said Yandex told the public in 2021 that Sasovo hosted two of its three supercomputers, built around Nvidia A100 chips and used to train its YandexGPT model. Yandex declined to say whether those machines were affected, and on Friday Reuters reported that the company was still assessing the damage and could not confirm whether the equipment can be restored.

That 2021 date matters. A machine Yandex described five years ago is not a fresh build, and the market it would be replaced from is the one Reuters describes next. Reuters notes that Sberbank, Yandex's main domestic rival, says Russian AI developers lag their US and Chinese counterparts by six to nine months and names sanctions-related difficulty importing advanced chips as the main bottleneck.

If the training cluster is damaged, the replacement cost is not a purchase order. It is a procurement problem with no listed supplier.

Inference is a different matter. Serving a model to users needs less interconnect than training one, and Yandex Cloud customers can be moved between zones, which is what the company told them to do. The training cluster cannot be moved the same way.

Knock-on effects outside Yandex

The outage reached customers who never signed a Yandex contract. Reuters listed technical issues at real estate aggregator Cian, book portal Litmarket, the Russian Railways website and the Spartak Moscow football club site. A state-owned bus company in the Moscow region said online ticket sales were unavailable because of a "temporary shutdown of a data centre."

The monitoring service Detector404 logged 58,268 user complaints over the previous day, according to Reuters. Yandex shares on the Moscow Exchange fell 3%.

Those figures measure annoyance, not capacity. Complaint counts spike on any visible outage, and a 3% share move on a stock that stands in for Russia's tech sector prices in more than one site.

Why the sites are now hidden

United24 Media, citing the Russian outlet Verstka, reported that Yandex has blurred all four of its Cloud data centres on Yandex Maps: Mytishchi in the Moscow region, Sasovo, Kaluga and Vladimir. The outlet said it was unclear when the concealment began. Yandex's own count is five large sites, so the list covers four of them, and the sources read for this piece do not identify the fifth.

Blurring a map tile protects nothing that a drone operator has already located. It does show that Yandex now treats the siting of its facilities as sensitive.

The wider pattern

Al Jazeera, relaying AFP and Reuters, wrote that Russia has hit several Ukrainian data centres and telecom facilities over the past month, including targets in central Kyiv, and that roughly 100,000 households lost internet temporarily after one attack. President Volodymyr Zelenskyy said on Thursday: "We always respond in mirror-like fashion." He added, "I can't share all the details."

Reuters said Ukraine's digital minister told it last month that the country was moving digital infrastructure underground. In August, Reuters said, President Vladimir Putin gave the state power to take control of critically important infrastructure judged poorly protected from drones. RBC, citing sources, reported that businesses are in talks with the government about building data centres in countries Moscow considers friendly.

Energised capacity is the constraint that decides how fast this plays out. The same logic runs through the site's reporting on Tesla's Project Sterling, where megawatts delivered, not megawatts announced, set the schedule. Open-weight models such as the one covered in the Qwen3.8-27B licence story show how much work a smaller cluster can do, which is the fallback a developer short of A100s will be weighing.

What would change my read is a Yandex statement that the Sasovo supercomputers were not in the damaged halls. The company has not made one, and it has not said when it expects an update.