Electrical computers and digital processing systems: memory – Storage accessing and control – Control technique
Reexamination Certificate
1998-08-13
2001-07-31
Ellis, Richard L. (Department: 2183)
Electrical computers and digital processing systems: memory
Storage accessing and control
Control technique
C711S006000, C711S165000, C707S793000
Reexamination Certificate
active
06269431
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to computer data storage backup, and more particularly, to a data storage system that provides backup of physical storage units with a minimum of host computer system involvement.
BACKGROUND OF THE INVENTION
Due to advances in computer technology, there has been an ever-increasing need for data storage in data processing networks. In a typical data processing network, there has been an increase in the number of volumes of data storage and an increase in the number of hosts needing access to the volumes. This has been especially true for networks of work stations. Not only have a greater number of workstations been added to the typical network, but also the increase in data processing capabilities of a typical workstation has required more data storage per workstation for enhanced graphics and video applications.
Fortunately for computer users, the cost of data storage has continued to decrease at a rate approximating the increase in need for storage. For example, economical and reliable data storage in a data network can be provided by a storage subsystem including a Redundant Array of Independent Disks (RAID). Presently it is practical to provide a single data storage subsystem with up to 20 terabytes (TB) of storage, or approximately 4000 logical volumes, using magnetic disk drives each having a storage capacity of 46 gigabytes.
Unfortunately for network administrators, the development of services for storage management has lagged behind the increase in storage to be managed. Consequently, the cost of storage management has become relatively more significant. More troubling is the difficulty of maintaining the same level of management service as the amount of storage increases. For example, users are accustomed to being provided with backup and restore services for their data that is stored on the network. Users are encouraged to store their data on the network so that it can be shared by other authorized users and maintained in a cost-effective manner in accordance with corporate document retention policies. However, data stored on the network is always subject to some chance of loss due to a severe failure of the data storage system. Backup and restore services are a conventional way of reducing the impact of data loss from the network storage. To be effective, however, the data should be backed up frequently, and the data should be restored rapidly from backup after the storage system failure. As the amount of storage on the network increases, it is more difficult to maintain the frequency of the data backups, and to restore the data rapidly after a storage system failure.
SUMMARY OF THE INVENTION
In accordance with one aspect of the invention, there is provided a method of permitting at least one host processor to obtain from a data storage subsystem access to backup versions. The data storage subsystem has primary data storage, and the backup versions are stored in secondary data storage linked to the data storage subsystem for transfer of the backup versions from the secondary data storage to the data storage subsystem. The method includes the host processor transmitting to the data storage subsystem a request for assignment of a virtual storage address from which a specified backup version in the secondary data storage can be accessed via storage access requests that are transmitted from the host processor to the data storage subsystem. The data storage subsystem responds to the request for assignment of a virtual storage address by assigning a virtual storage address from which the specified backup version in the secondary data storage can be accessed via storage access requests that are transmitted from the host processor to the data storage subsystem. The host processor accesses the specified backup version by transmitting to the data storage subsystem storage access requests that specify the assigned virtual storage address and that specify portions of the specified backup version to be accessed. The data storage subsystem responds to the storage access requests by accessing the specified portions of the specified backup version to be accessed.
In accordance with another aspect, the invention provides a machine-readable program storage device containing a program for a storage controller of a data storage subsystem permitting at least one host processor to obtain from the data storage subsystem access to backup versions that are stored in secondary data storage linked to the data storage subsystem for transfer of the backup versions from the secondary data storage to the data storage subsystem. The program is executable by the storage controller for receiving from the host processor a request for assignment of a virtual storage address from which a specified backup version in the secondary data storage can be accessed via storage access requests that are transmitted from the host processor to the data storage subsystem. The program is also executable by the storage controller for responding to the request for assignment of a virtual storage address by assigning a virtual storage address from which the specified backup version in the secondary data storage can be accessed via storage access requests that are transmitted from the host processor to the data storage subsystem. The program is further executable by the storage controller for receiving from the host processor storage access requests that specify the assigned virtual storage address and that specify portions of the specified backup version to be accessed, and for responding to the data storage access requests by accessing the specified portions of the specified backup version to be accessed.
In accordance with yet another aspect, the invention provides a machine readable program storage device containing a program for a storage controller for a data storage subsystem permitting at least one host processor to obtain from the data storage subsystem access to backup versions that are stored in secondary data storage linked to the data storage subsystem for transfer of the backup version from the secondary data storage to the data storage subsystem. The program is executable by the storage controller for receiving from the host processor a request for allocation of spare data storage from which a specified backup version can be accessed via storage access requests transmitted from the host processor to the data storage subsystem, and responding to the request from the host processor for allocation of the spare data storage by associating a virtual storage address with the specified backup version, and checking whether or not spare data storage is available in the data storage subsystem for storage of the specified backup version, and when spare data storage is available in the data storage subsystem for storage of the specified backup version, allocating the spare data storage for storing the specified backup version, mapping the virtual storage address to an address of the spare data storage allocated for storing the specified backup version, and transmitting a copy of the specified backup version from the secondary data storage to the spare data storage allocated for storing the specified backup version. The program is further executable by the storage controller for receiving from the host processor storage access requests specifying the virtual storage address; and responding to the storage access requests from the host processor by checking whether or not there is a mapping of the specified virtual storage address to data storage in the data storage subsystem, and when there is a mapping of the specified virtual storage address to data storage in the data storage subsystem, accessing the data storage in the data storage subsystem to which the virtual storage address is mapped, and when there is not a mapping of the specified virtual storage address to data storage in the data storage subsystem, then accessing the specified backup version associated with the virtual storage address by accessing the secondary data storage.
In accordance with s
Ellis Richard L.
EMC Corporation
Howrey Simon Arnold & White , LLP
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