Server is now back on-line and all services are operational. A full data recovery was necessary and took most of the night.
13th November 2017
Suspect problem with kernel
The problem seems to come from the last kernel security upgrade we pushed on the server. This new kernel doesn't play well with aliyun virtual servers. Fastest recovery solution is to start a new instance and recover dat from backups/snapshots
Close support ticket with Aliyun
Aliyun support cannot find anything wrong with the disk or server, they suggest to try a recovery through snapshot of the surrent disk and starting fresh.
Opened support ticket with Aliyun
Opened a support ticket with Aliyun to get help on the server issue, suspect a disk problem.
Data access outage (API, views)
Main data server cannot reboot after security upgrade maintenance