Dynamic snapshot mounting

摘要

Techniques are presented for keeping only the most commonly-accessed snapshots mounted at any given time, while providing for fast mounting of unmounted snapshots. Techniques are also provided for maintaining separate databases for the snapshots of each primary filesystem in order to minimize locking latency.

主权项

1. A method of dynamically mounting and unmounting a set of snapshot file systems (SFSs) stored within a data storage system, each SFS of the set of SFSs associated with a corresponding primary file system (PFS) of a set of PFSs stored within the data storage system, each SFS representing a state of its corresponding PFS at a particular prior point in time, the method comprising:
mounting a strict subset of the set of SFSs on the data storage system, the strict subset of the set of SFSs having a number of elements not exceeding a maximum number of snapshots; receiving a request to access an additional SFS not within the strict subset of the set of SFSs; mounting the additional SFS on the data storage system, thereby adding the additional SFS to the strict subset of the set of SFSs; and if mounting the additional SFS on the data storage system causes the number of elements of the strict subset of the set of SFSs to exceed the maximum number of snapshots, then, in response, unmounting another SFS of the strict subset of the set of SFSs from the data storage system, thereby removing the other SFS from the strict subset of the set of SFSs;wherein mounting the additional SFS on the data storage system includes:
generating a new filesystem object; reading metadata of the additional SFS from a file stored within the PFS corresponding to the additional SFS; and storing the read metadata within the new filesystem object.