1. A method for coordinating point-in-time snapshots among multiple computing platforms, the method comprising: receiving a notification from an agent on a first computing platform indicating a time when a snapshot of the first computing platform's data storage was performed; receiving a notification from an agent on a second computing platform indicating a time when a snapshot of the second computing platform's data storage was performed; determining that the time when the snapshot of the second computing platform's data storage was performed is later than the time when the snapshot of the first computing platform's data storage was performed; notifying the agent on the first computing platform of the time when the snapshot of the second computing platform's data storage was performed; and receiving from the agent on the first computing platform a report of any location in the first computing platform's data storage to which data were written after the time when the snapshot of the first computing platform's data storage was performed and responsive to a write request that was made prior to or including the time when the snapshot of the second computing platform's data storage was performed.