Method and device for achieving copy-on-write snapshot

Abstract

The invention discloses an improved method for achieving copy-on-write (COW) snapshot, which comprises the following steps: setting up the bitmaps for a source data area and a snapshot area, wherein each bit in the bitmap corresponds to N data blocks; and indicating that data are written in the corresponding data blocks if the bit is valid, and if not, indicating that the data are not written in the corresponding data blocks, wherein N represents a natural number. Based on the bitmaps for the source data area and the snapshot area, the following functions can be performed: when a writing request is received by the source data area, whether the corresponding data blocks are required to be copied to the snapshot data area is judged, and the copy operation is carried out only when necessary. The invention further discloses an improved device for achieving the copy-on-write snapshot. The improved scheme provided by the invention is capable of directly responding to most writing request of a host computer instead of copying the data blocks to the snapshot data area. By making the improvement, the invention can reduce the delay in the writing request of a user, reduce the size of the snapshot citation index and the snapshot data area and increase the utilization rate of the memory space.

Description

technical field [0001] The invention relates to the technical field of computer storage, in particular to an improved implementation method and device for copy-on-write snapshots. Background technique [0002] With the accelerated development of information technology, the scale of key business data of enterprises is increasing day by day. Enterprises not only require larger and larger storage capacity, but also have higher and higher requirements for data security. With the improvement of storage application requirements, users need online backup and data protection. A snapshot (Snapshot) technology is an effective online data protection method, which can quickly realize online data backup. [0003] A snapshot is a fully available copy of a specified data set, which includes an image of the specified data set at a certain point in time. The specified data collection is called the source data area, and the image at a certain point in time is called the snapshot data area. ...

AI Technical Summary

Problems solved by technology

[0027] Although copy-on-write snapshots are created quickly and only need to save the changed data blocks in the source data area, the space usage rate is also low. However, when the data blocks in the source data area are changed for the first time, the The data block is backed up to the snapshot data area and the snapshot reference pointer is established in the memory before the data block can be updated, which brings a large delay to the user's write request; at the same time, as more and more data is changed in the source data area, The memory consumed by the snapshot reference index will become larger and larger, and the storage space occupied by the snapshot data area will also increase, which will bring a great burden to the storage system

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