Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1998-06-12
2001-02-13
Homere, Jean R. (Department: 2777)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000, C707S793000, C707S793000, C707S793000
Reexamination Certificate
active
06189016
ABSTRACT:
COPYRIGHT NOTICE/PERMISSION
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. The following notice applies to the software and data as described below and in the drawing hereto: Copyright®1998, Microsoft Corporation, All Rights Reserved.
TECHNICAL FIELD OF THE INVENTION
This invention relates generally to data storage in digital computers, and more particularly to recording changes to files or file attributes in a storage volume.
BACKGROUND OF THE INVENTION
A self-contained unit of storage in a computer system is often referred to as a “volume.” Files systems administer the storage in volumes by allocating it to files and directories in response to appropriate requests. Over time, files and directories are modified in different manners. For example, directories are created and renamed. Files are created and deleted and the data in a file or in one of its attributes can be modified. Files systems reflect these changes to their base entities by modifying appropriate attributes of the entities, like creation date and size.
To track and determine what modifications have happened in a volume, traditional storage management applications have to traverse the name space of the entities in the volume verifying whether attributes of interest (like the size or the last modified date) have changed. This means that, in the absence of any additional mechanism, applications need to roam through the name space of a volume and detect changes by inspecting the appropriate attributes of a file or a directory.
There are several drawbacks to this traditional mechanism. First, when the number of entities in the volume grows, the time to visit them grows. Second the act of traversing the name space affects the contents of the in-memory caches. Given that there is no re-use of the information visited any displacement from the cache of other useful information is detrimental to the over-all performance of the system. Third, the I/O activity required to retrieve the needed attribute information is mostly random. The two main consequences are that, first, the number of disk seeks required to traverse the name space is proportional to the number of entities, thus it takes increasingly longer to do it. Second, this I/O activity has the potential effect of disturbing any other kind of I/O that is happening in the volume.
The Windows® operating system includes a mechanism that tries to address the above problem. This mechanism allows an entity to register for an event that will trigger when a change happens at a directory or at a file. This will, in effect, eliminate the need to traverse the appropriate subset of the name space. The serious drawback of this mechanism is that for each file or directory of interest, an individual event needs to be registered. This does not scale well, as the NT kernel needs to track an ever-increasing number of events to notify on.
Thus, there remains a need for a more efficient, scalable and powerful approach to tracking modifications to a storage volume in a computer system.
SUMMARY OF THE INVENTION
The present invention provides a system for keeping a time-ordered change journal of all the changes that happen in a storage volume. Important changes, such as user-driven changes, to a file or to a directory in a volume are detected and recorded. According to one aspect, a computer-readable change journal is kept for a storage volume. The change journal has a plurality of change records each having a unique identification that unambiguously specifies the order in which the records were created, wherein each change record records one or more changes to a file in a computer-readable storage volume. Each change record is created in response to selected types of changes to the file in the storage volume, and each records one or more reasons why the file was changed. In addition, an entry is made for the file in an index of files on the storage volume, with the entry providing a reference to the unique identification for the change record, to allow the most recent change record for a file to be identified from the index.
According to another aspect of the invention, there is provided a data structure comprising a computer-readable change journal stored on a computer-readable carrier. The change journal has a plurality of change records each having a unique identification that unambiguously specifies the order in which the records were created, wherein each change record records one or more changes to a file in a computer-readable storage volume. Further, each change record specifies one or more reasons why the file was changed. Additionally, the data structure includes an entry for the file in an index of files on the storage volume, with the entry referencing the unique identification for the change record.
According to other aspects, the invention is embodied in a file system and in an operating system.
REFERENCES:
patent: 4819156 (1989-04-01), DeLorme et al.
patent: 4823261 (1989-04-01), Bank et al.
patent: 5600834 (1997-02-01), Howard
patent: 5603024 (1997-02-01), Goldring
patent: 5706509 (1998-01-01), Tso
patent: 5748985 (1998-05-01), Kanai
patent: 5758355 (1998-05-01), Buchanan
patent: 5806058 (1998-09-01), Mori et al.
patent: 5873096 (1999-02-01), Lim et al.
patent: 5907848 (1999-05-01), Zaiken et al.
patent: 5974425 (1999-10-01), Obermarck et al.
patent: 5974429 (1999-10-01), Strub et al.
patent: 6026412 (2000-02-01), Sockut et al.
Andrew Brian D.
Cabrera Luis Felipe
Kimura Gary D.
Miller Thomas J.
Zbikowski Mark J.
Homere Jean R.
Microsoft Corporation
Schwegman Lundberg Woessner & Kluth P.A.
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