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RECONCILING A FILE SYSTEM TO A POINT IN TIME USING INCREMENTAL BACKUP DATA

IP.com Disclosure Number: IPCOM000014877D
Original Publication Date: 2000-Feb-01
Included in the Prior Art Database: 2003-Jun-20
Document File: 3 page(s) / 37K

Publishing Venue

IBM

Abstract

An algorithm is described that reconciles a client file system to its state at a specified point in time using incremental backup data stored on a storage-management server. This is accomplished by restoring selected files from the server to the client and by deleting selected files from the client file system. After the algorithm has been executed, the client file system corresponds to its state at the desired point in time. In a typical embodiment, this algorithm is used in a client-server system. A storage-management server stores objects that have been backed up or archived from various client nodes. The server stores client data in a storage hierarchy consisting of various media types (e.g., disk, tape, optical) and uses a database for tracking the attributes and storage location of each client object. Traditionally, the client and server operate in the following distinct modes. In one mode of operation, the client and server cooperate to perform an incremental backup. In this operation, the client examines a file system and sends to the server a copy of each file that has not previously been backed up to the server or that has been modified since the last backup. For each file received during an incremental backup, the server stores the file in its storage hierarchy and also stores meta-data about that file in its database. Incremental backup allows each individual file to be cataloged by the server and allows any or all such files to be restored to the server. However, incremental backup and restore can be inefficient because each file must be processed individually by both the client and the server. This inefficiency can be problematic during a restore of an entire file system, since critical time may be lost as each file is restored individually. In an alternate mode of operation, the client and server may perform an image backup. In this operation, the client creates an image of the entire file system and sends this image to the server as a single object. If the entire file system must be restored to the client, the server can send the file system image and the client then processes this image to re-create the file system as it existed at the time the image was created. Image backup and restore operations are efficient because handling of individual files is greatly reduced. However, any changes to the file system after the image was created will not be reflected in the restored file system.

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  RECONCILING A FILE SYSTEM TO A POINT IN TIME USING INCREMENTAL BACKUP DATA

An algorithm is described that reconciles a client file system to its state at
a specified point in time using incremental backup data stored on a
storage-management server. This is accomplished by restoring selected files
from the server to the client and by deleting selected files from the client
file system. After the algorithm has been executed, the client file system
corresponds to its state at the desired point in time.

In a typical embodiment, this algorithm is used in a client-server system. A
storage-management server stores objects that have been backed up or archived
from various client nodes. The server stores client data in a storage
hierarchy consisting of various media types (e.g., disk, tape, optical) and
uses a database for tracking the attributes and storage location of each
client object. Traditionally, the client and server operate in the following
distinct modes.

In one mode of operation, the client and server cooperate to perform an
incremental backup. In this operation, the client examines a file system
and sends to the server a copy of each file that has not previously been
backed up to the server or that has been modified since the last backup.
For each file received during an incremental backup, the server stores the
file in its storage hierarchy and also stores meta-data about that file in
its database. Incremental backup allows each individual file to be
cataloged by the server and allows any or all such files to be restored to
the server. However, incremental backup and restore can be inefficient
because each file must be processed individually by both the client and the
server. This inefficiency can be problematic during a restore of an
entire file system, since critical time may be lost as each file is
restored individually.

In an alternate mode of operation, the client and server may perform an
image backup. In this operation, the client creates an image of the entire
file system and sends this image to the server as a single object. If the
entire file system must be restored to the client, the server can send the
file system image and the client then processes this image to re-create the
file system as it existed at the time the image was created. Image backup
and restore operations are efficient because handling of individual files
is greatly reduced. However, any changes to the file system after the
image was created will not be reflected in the restored file system.

In a typical embodiment of this invention as described below, incremental and
image backup and restore operations are combined to achieve certain benefits
of both operating modes. Specifically, the invention involves restoring a
file system image and then reconciling the restored file system so that it
matches its state at a specified point in time. This approach affords much of
the efficiency inherent in an image restore while still allowing the file
system to be restored to the state in which i...