1. Technical Field
This application generally relates to a data storage system, and more particularly to techniques using consistency points and associated consistent copies of data in a data storage system.
2. Description of Related Art
Computer systems may include different resources used by one or more host processors. Resources and host processors in a computer system may be interconnected by one or more communication connections. These resources may include, for example, data storage devices such as those included in the data storage systems manufactured by EMC Corporation. These data storage systems may be coupled to one or more host processors and provide storage services to each host processor. Multiple data storage systems from one or more different vendors may be connected and may provide common data storage for one or more host processors in a computer system.
Different tasks may be performed in connection with a data storage system. For example, processing may be performed in a data storage system for creating and maintaining a mirror copy of data from a source system at a target system. As file operations are performed which cause a data modification to the source system, the modifications may be recorded and then applied to the target system's copy of the data. In connection with performing data operations, it may be desirable to utilize a copy of the data on the target system when the data is in a consistent state. The source or target system may be characterized as being in a consistent state at a point in time, for example, when all outstanding database transactions are committed, any new incoming transactions are placed on hold or “queued”, and any database buffers are flushed with respect to the selected point in time. However, it may be difficult to establish and determine when the copy of the data on the target system is in such a consistent state.
Thus, it may be desirable to have an efficient technique for providing a consistent copy of data on the target system and for determining when the copy of the data on the target system is in a consistent state while minimizing any negative impact on the data of the source system and applications accessing the data on the source system.