Brian L Stuart: An O(1) Method for Storage Snapshots
The capability of taking snapshots is approaching
ubiquity as a feature of file systems and data storage
arrays. Here, we present an approach to structuring and
managing snapshots in a storage space that provides for
rapid creation and roll-back. This approach has been
realized in the form of a Plan 9 kernel device that can
be interposed between any pair of storage service and
application. The kernel device has, in turn, been used
to support an experimental file system. In this paper,
we discuss the basic snapshot model, its implementation,
and its application to a file system. Finally, we
consider extensions to the model for supporting the