Potential impact of DST changes on custom DFS Replication schedules

First published on TECHNET on Mar 08, 2007
If you have custom replication schedules configured that will be in place on Sunday, March 11 at 2AM when DST kicks in, consider the following scenario:

• DFS Replication is configured to block replication on Sundays except at 2AM Local Time.
• File object was created/modified on a DFSR member outside the replication allow window on Saturday, March 10.
• Now time goes forward into the DST change period at 2AM on Sunday March 11. The local system time on the DFSR members go from 1:59:59AM to 3:00:00AM.

Note how the schedule has not arbitrarily changed to make the replication window 3AM. DFSR does not make any adjustments like AD and FRS replication.
Some queued data may replicate during the few seconds of delta between servers (DFSR is very fast, and if the amount of changes is very low, you can expect some of it to replicate - also remember that this is pull replication and the downstream may be slightly different in time than the upstream), but there is no guarantee any data will replicate in this missed 2AM window. In fact, any files created after the window was 'lost' definitely will not be replicated until the next window opens it will be as if the 2AM window never happened. The schedule must be manually adjusted by admins in order to avoid a missed replication window.

--Ned Pyle