These four servers will be taken down on Sunday October 3rd  to fix a problem with the RAID controller. The downtime should be less than 1h. Web50 will be taken down at 5pm UTC, Web56 at 5.30pm  UTC, Web65 at 5pm UTC and Web83 at 6pm UTC.
[17:20 UTC] Update: We are bringing Web50 down.
[17:55 UTC] Update: Web50 is up and running again.
Update: All four servers have now been fixed