Importance

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Abstract

A data storage subsystem employs managed files, each comprising one or an aggregation of multiple constituent user files, to reduce file management overhead costs. After receiving user files from a client station, the subsystem creates a contiguous managed file by aggregating selected ones of the received user files according to certain predetermined criteria. Managed file creation and use are transparent to the client stations. Eventually, unused or 'deleted-file space' arises as individual user files are deleted from their respective managed files. 'Reclamation' is triggered when the amount of deleted-file space in a prescribed storage area (e.g. device, volume, managed file, etc.) satisfies certain criteria, e.g. poor data storage efficiency. Reclamation is performed to regain wasted space between managed files, and also space that occurs within managed files due to deletion of some but not all constituent user files. Reclamation is applied to the prescribed storage area one managed file at a time. Each managed file is reviewed to determine whether it contains any deleted-file space. Managed files without any deleted-file space are simply copied intact to the target storage area. If a managed file contains deleted-file space, however, a 'reconstruction' process is performed for that file. Reconstruction identifies any contiguous regions of user files within the managed file, then copies the contiguous regions to adjacent locations in a target storage area. Reclamation is complete after all managed files in the prescribed data storage area have been copied or reconstructed.

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First Claim