Continuous backup using a mirror device

Abstract

Providing continuous backup of a storage device includes subdividing the storage device into subsections, providing a mirror device of the storage device that contains a copy of data that is on the storage device when the continuous backup is initiated, providing a time indicator that is modified periodically, and, in response to a request to write new data to a particular subsection of the storage device at a particular time, maintaining data being overwritten by the new data according to the particular subsection and according to a value of the indicator at the particular time, where, for a first write after the continuous backup is initiated, data from the mirror device is used to maintain data being overwritten. The subsections may be tracks. Maintaining the data being overwritten may include constructing a linked list of portions of data for each of the subsections. The portions of data may have variable sizes.

Description

BACKGROUND OF THE INVENTION [0001] 1. Technical Field [0002] This application relates to computer storage devices, and more particularly to the field of selectively maintaining and modifying portions of data stored on a computer storage device and corresponding to particular points in time. [0003] 2. Description of Related Art [0004] Host processor systems may store and retrieve data using a storage device containing a plurality of host interface units (host adapters), disk drives, and disk interface units (disk adapters). Such storage devices are provided, for example, by EMC Corporation of Hopkinton, Mass. and disclosed in U.S. Pat. No. 5,206,939 to Yanai et al., U.S. Pat. No. 5,778,394 to Galtzur et al., U.S. Pat. No. 5,845,147 to Vishlitzky et al., and U.S. Pat. No. 5,857,208 to Ofek. The host systems access the storage device through a plurality of channels provided therewith. Host systems provide data and access control information through the channels of the storage device an...

AI Technical Summary

Benefits of technology

The present invention provides a method for providing continuous backup of a storage device by subdividing the storage device into subsections and maintaining data being overwritten by new data according to the subsection and a value of a time indicator. The method includes constructing a linked list of portions of data for each subsection, combining data for two data write operations if they are a subset of each other, and restoring the storage device to a state at a particular point in time by writing the maintained data to the storage device. The invention also includes computer software that obtains a value of a time indicator that is modified periodically and maintains data being overwritten by new data according to the subsection and the value of the indicator. The technical effect of the invention is to provide a reliable and efficient method for continuous backup of a storage device.

Problems solved by technology

There are a number of drawbacks to such data backup services, including the fact that it is only possible to recover data that corresponds to data that was saved at a periodic backup.

For example, if data is backed up at 9:00 a.m. and 3:00 p.m. daily, then a user is not able to recover data from, say, 11:00 a.m.

However, increasing the frequency of backups increases the storage requirements for backup data and increases the overhead and complexity of the backup data.

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