System and method for generating a point-in-time copy of a subset of a collectively-managed set of data items

摘要

Various systems and methods selectively generate a point-in-time copy of less than all of the data items within a collectively-managed set of data items. One method involves detecting a modification to a first unit of data within a collectively managed set, subsequent to generation of a selective snapshot of the collectively managed set, and then accesses a first tag associated with the first unit of data. Based on a value of the first tag, the method determines whether the first unit of data is included in a subset of the collectively managed set. The subset includes at least two of the units of data and fewer than all of the units of data in the collectively managed set. Based upon whether the unit of data is included in the subset, the method selects whether to preserve an original value of the first unit of data.

主权项

1. A method comprising:
receiving a request to generate a selective snapshot of a collectively managed set of data, wherein
the request comprises an identifying tag to identify an identified subset of the collectively managed set of data, andthe identifying tag is one of a plurality of tags; generating the selective snapshot of the collectively managed set of data, wherein the selective snapshot comprises a snapshot inode for each unit of data within the collectively managed set of data; detecting a modification to a first unit of data within the collectively managed set of data, wherein
a first tag is assigned to the first unit of data,the detecting occurs subsequent to the generation of the selective snapshot of the collectively managed set of data, andthe first tag identifies a first subset of the collectively managed set of data; based on a comparison of the first tag to the identifying tag, determining whether the first unit of data is included in the identified subset of the collectively managed set of data, wherein
the identified subset comprises at least two of the units of data and fewer than all of the units of data in the collectively managed set of data; based upon whether the first unit of data is included in the identified subset, selecting whether to preserve an original value of the first unit of data, wherein
the original value is a value of the first unit of data at a point in time at which the selective snapshot was generated,the selecting occurs subsequent to generation of the selective snapshot of the collectively managed set of data, andthe selecting is performed by a computing device implementing a selective snapshot module; wherein the determining comprises determining that the first unit of data is not included in the identified subset, and wherein the selecting comprises selecting to not preserve the original value of the first unit of data; wherein the determining comprises determining that the first unit of data is included in the identified subset, and wherein the selecting comprises selecting to preserve the original value of the first unit of data; and transferring the original value of the first unit of data to the snapshot inode for the first unit of data.