Associating events with the state of a data set

In a data storage system, events are associated with the state of a data set at specific points in time, the data set being a collection of addressable storage that is modified by a host computer system writing to specific addresses, by capturing copies of writes made by the host to the data set, each copied write having write data and address. Sequence information is assigned to the captured writes to organize the captured writes in the time sequence in which the writes were captured. Absolute time information is assigned to each captured write. Each captured write is retained as an entry in a repository, the entry including write data, address, sequence information, and absolute time information. An event is associated to a specific entry in the repository. The association is retained for subsequent use.