A method for accessing virtual storage medium

Abstract

The invention discloses a virtual storage medium access method. The method includes the steps of conducting accessing at the position O of the virtual storage medium, calculating a storage unit number U which the position in the virtual storage medium belongs to according to the position O, calculating a second-stage index table page number P which the position belongs to according to the storage unit number, finding a first-stage index table corresponding item according to the second-stage index table page number P to obtain a storage unit number Up corresponding to a second-stage index table page in a mapping file, finding a storage unit number Uo corresponding to the position O of the virtual storage medium in the mapping file from the second-stage index table page P according to the storage unit number U, and conducting accessing on the storage unit Uo in the mapping file. Through two stages of indexing, the mapping relation of all storage units in the virtual storage medium and all storage units in the mapping file is finally determined. Through a virtual storage medium access method, the waste of unnecessary physical storage space can be sufficiently reduced, and good access performance is achieved.

Description

technical field [0001] The invention relates to the technical field of computer data access, in particular to a virtual storage medium access method. Background technique [0002] The initial virtual storage medium uses an image file to store data, and the positions in the virtual storage medium correspond to the positions in the image file one by one, and the access to the virtual storage medium is directly mapped to the access to the image file. This access method is easy to implement, and the access efficiency is closer to that of physical storage, but the size of the image file is the same as the capacity of the virtual storage medium, which requires a large amount of storage space. [0003] In order to reduce unnecessary storage space, a discontinuous mapping method can be used, only the data written in the virtual storage medium is stored in the image file, and a mapping table is established to record the corresponding relationship between the virtual storage medium an...

AI Technical Summary

Problems solved by technology

[0004] The above method can reduce the occupation of unnecessary storage space to a certain extent, but there are still some limitations: when the capacity of the virtual storage medium is large (above TB level), the access performance is not good, and when the actual storage data volume When it is small, the wasted space for storing the mapping table is large

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