Hello and apologies for the short notice.

We are required to put HDFS into safe mode at approximately 13:50 UTC today, which means that the file system will be read-only.

This might be for as little as 30 minutes, but the  maintenance window we're working within is for up to 2 hours, so the actual period of read-only access will depend on the outcome of the eqiad row A switches upgrade (https://phabricator.wikimedia.org/T329073) by the Infrastructure Foundations team.

We will be pausing ingestion to the Data Lake a little ahead of this time, so there will be a delay in dataset availability on HDFS, Cassandra, and Druid etc.

Apologies for any inconvenience that this disruption to service will cause you.

Please do let us know by reply to this list or in #wikimedia-analytics on IRC if you have any queries, or would like to follow-along with our support of the maintenance work.

Kind regards, Ben Tullis