Since you are an admin of a Salesforce org with at least one sandbox currently on CS1, CS2, CS4, CS22, CS24, CS27, CS28, CS41, and/or CS43, we want to inform you of an upcoming maintenance on October 20, 2018 that involves moving these instances to other data centers within the same region.
In order to provide exceptional performance, availability, and reliability of our service, we occasionally need to perform a capacity planning activity, called a sandbox migration. The CS1, CS2, CS4, CS22, CS24, CS27, CS28, CS41, and CS43 instances will be moving from an existing Salesforce sandbox instance onto new infrastructure. Following the maintenance, these sandbox instances will continue to be served from the United States in our data centers located in the Phoenix, Arizona and Washington, DC metropolitan areas. The sandbox instance names will not change.
The CS1, CS2, CS4, CS22, CS24, CS27, CS28, CS41, and CS43 sandbox migrations will take place on:
October 20, 2018, 23:00 - 00:30 UTC
During the maintenance, your sandbox(es) will be available in read-only mode.
NOTE: If you refresh your sandbox between now and October 20, 2018, there is a chance your new sandbox copy may still be placed on a migrating sandbox instance.
If your corporate network settings or email security filters restrict access to IP ranges, please ensure that you include the current Salesforce IP ranges. Otherwise, your users may be unable to access the sandbox following the migration. Take note of the July 2018 additions made to this article.