In brief

• Yandex says it recovered 97.16% of Yandex Cloud customer data after Ukrainian drone strikes on its data centers in October.
• The remaining 2.84% is permanently lost, which the company attributes to equipment damage and missing backups on the platform.
• Customers who used Yandex's backup tools lost no data, and automatic backups are now enabled by default for new servers.

Permanent loss for a small share of customers

Yandex said engineers restored access to 97.16% of the client data stored in Yandex Cloud after the attacks. The company said the remaining 2.84% cannot be recovered because of severe equipment damage and because some customers did not keep external backups on the platform (Yandex potwierdził nieodwracalną utratę części danych klientów. To skutek ukraińskich ataków – Onet) («Яндекс» признал, что после украинских атак не может восстановить почти 3% клиентских данных в Yandex Cloud – Meduza) («Яндекс» не сможет восстановить почти 3% клиентских данных Yandex Cloud после атак на дата-центры – TV Rain). Yandex put the figure in a press release issued on Tuesday (Nearly 3% of Cloud Customer Data Permanently Lost After Drone Strikes, Yandex Says – The Moscow Times).

What happened to the data centers

Ukrainian drones struck several Yandex data centers between October 8 and October 11. The sites in Sasovo in the Ryazan region, Kaluga and Vladimir were hit, and all three stopped operating ("Аліса" від "Яндекса" стала дурнішою після українських ударів по дата-центрах: росіяни масово скаржаться на збої "розумної колонки" – Espreso). Yandex Cloud was switched to emergency mode and two availability zones went offline. The disruption reached ride-hailing, car-sharing, food delivery, online maps, email, banking and streaming services, as well as government agencies and private firms that rely on Yandex infrastructure.

Backups and changes to the platform

Customers who had enabled automated backup features reported no data loss, the company said. To prevent similar gaps, Yandex has made automatic data copies the default setting for every newly created virtual cloud server. It also launched a new availability zone, ru-central1-f, in another location to make services more resilient to failures.

Impact on Alice assistant

Users of Yandex's Alice voice assistant have complained of freezes, search errors and mispronounced Russian words since the attacks, according to posts in the service's Telegram channel («Алиса» от «Яндекса» поглупела после украинских ударов по дата-центрам – Charter 97). Complaint counts on DownDetector have risen roughly fivefold over the past two weeks.

Recovery outlook

A report cited by Kommersant estimated that replacing damaged equipment at the data centers could take about half a year. After the strikes, Yandex moved its three supercomputers to a new location and withdrew its annual revenue forecast.