Block-level snapshot system and user reading and writing method based on same

Abstract

The invention provides a block-level snapshot system, which comprises a snapshot device chain formed by a source device and one or more than one snapshot device, wherein the source device and the snapshot device consist of a cache device, a pair of block devices SDU (service data unit) and SDL (standard description language), and a storage device. The block device SDU is used for receiving and processing a reading and writing request of a user on a system, the cache device is used for processing the reading and writing request of the user forwarded from the block device SDU and is used for caching data, and the block device SDL is used for processing a reading request forwarded from the cache device. When the reading request of the user is received by the system, the reading request which is not of local data is forwarded to the block device SDU of a previous time point by the block device SDU; and the reading request which is of local data is read from the storage device and is returned to the cache device for caching by the block device SDL. The cache device is only used for caching the data locally stored, and thus the problem of the redundancy of cache resource is solved.

Description

technical field [0001] The invention relates to the technical field of snapshots, in particular to a block-level snapshot system and a user reading and writing method based on the system. Background technique [0002] According to the definition of the Storage Network Industry Association (SNIA), a snapshot (Snapshot) is a fully available copy of a specified data set, which includes an image of the corresponding data at a certain point in time. [0003] With the maturity of snapshot technology, many snapshot systems and prototype systems have emerged at home and abroad, including the LVM (Logical Volume Manager) snapshot that comes with the Linux kernel, EMC's TimeFinder, IBM's ESS FlashCopy, or Netapp's WAFL snapshots and more. In these snapshot products or prototype systems, both the snapshot device and the source device are available to users in the form of virtual devices. The snapshot device essentially provides another access path to the data in the source device. I...

AI Technical Summary

Problems solved by technology

Cache redundancy means the waste of cache resources, which in turn affects the storage performance of the system

[0004] Figure 1A shows a schematic diagram of the LVM snapshot system. LVM is a system for managing disk partitions that comes with the linux system. Although the system supports snapshots, its snapshots will cause cache redundancy problems: after creating a read-only snapshot at a certain moment, The source and the read-only snapshot share data blocks 1, 2, and 3 in the physical space (as shown in Figure 1A)

exist Figure 1B In the illustrated embodiment, when the user reads data block 2 from the source and the read-only snapshot, data block 2 will store two copies in the cache, resulting in a cache redundancy problem

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