Abstract: Disclosed is a method and apparatus for refreshing a copy of a data volume. In one embodiment of the method first and second data portions of a data volume are copied to first and second memory blocks, respectively, of a memory coupled to a computer system. First and second bits of a first map stored in memory are then set, wherein the first and second bits correspond to the first and second memory blocks, respectively. The first data portion of the data volume is modified after the first data portion is copied to the first memory block. A first bit in a second map stored in memory is set after data of the first data portion is modified. An instruction is generated to refresh the data contents of the first and second memory blocks. The first bit of the first map is cleared in response to generation of the refresh instruction.

Abstract: System and method for maintaining temporal data in data storage at the logical device level. Embodiments of the temporal volume manager may provide an interface that allows applications and/or application agents to communicate with the temporal volume manager to manage and keep track of the temporal information on one or more temporal volumes. Embodiments may provide an infrastructure for applications that work on the history of data such as temporal databases, versioning file-systems/repositories, data archives, and streaming media to manage temporal data. In one embodiment, if an application does not want to use the temporal volume directly, application agents may be used to access the temporal volume. Embodiments may provide I/O controlled, application-controlled, and/or periodic checkpointing of temporal data on the temporal volume. One embodiment may provide a mechanism for generating temporal images (e.g.

Abstract: A method and system of providing cascaded replication is disclosed. According to one embodiment a method is provided in which data to be written to a data volume of a first node is replicated to a data volume of a second node and data to be written to the data volume of the second node is replicated to a data volume of a third node where at least one of the replication operations includes asynchronous data replication.

Abstract: Disclosed is a method for creating a virtual copy of data stored in a first memory. The virtual copy of data stored in the first memory is created in a second memory in response to a request to create a copy of all data stored in the first memory. Creating the virtual copy includes, in one embodiment, creating first and second tables in memory each one of which comprises a plurality of multibit entries. Each entry of the first table corresponds to a respective memory region of the first memory. Each entry of the second table corresponds to a respective memory region of the second memory. Each first bit of the first table indicates whether the corresponding memory region of the first memory contains valid data. Each second bit of the first table indicates whether data in the corresponding memory region of the first memory has been modified since the first table was created.

Abstract: A virtual copy of data stored in a first memory is created in a second memory. Creating the virtual copy includes, in one embodiment, creating first and second tables in memory each one of which comprises a plurality of multibit entries. Each entry of the first table corresponds to a respective memory region of the first memory. Each entry of the second table corresponds to a respective memory region of the second memory. The first bit of the first and second tables indicates whether the corresponding memory region of the first and second memories, respectively, contains valid data. The second bit of the first and second tables indicates whether data in the corresponding memory region of the first and second memories, respectively, has been modified since the creation of the first and second tables, respectively.

Abstract: Disclosed is a method and apparatus for refreshing a copy of a data volume. In one embodiment of the method first and second data portions of a data volume are copied to first and second memory blocks, respectively, of a memory coupled to a computer system. First and second bits of a first map stored in memory are then set, wherein the first and second bits correspond to the first and second memory blocks, respectively. The first data portion of the data volume is modified after the first data portion is copied to the first memory block. A first bit in a second map stored in memory is set after data of the first data portion is modified. An instruction is generated to refresh the data contents of the first and second memory blocks. The first bit of the first map is cleared in response to generation of the refresh instruction.