Hi,
We're about to apply necessary schema changes for Wikimedia's MediaWiki 1.17 upgrade to the Toolserver databases. We will apply the changes to one server for each cluster at once; while the primary server is being updated, user databases will be unavailable, but replication won't be interrupted.
The exception is s2/s5, which currently only has one server. Databases on these clusters will not be replicated and might be partially unavailable during the maintenance.
This was not announced in advance since we only learnt about the changes about 10 minutes ago. Sorry.
- river.