System and method for disk control with snapshot feature including read-write snapshot half

• US 6,341,341 B1
• Filed: 12/16/1999
• Issued: 01/22/2002
• Est. Priority Date: 12/16/1999
• Status: Expired due to Term

• Current Assignee: RPX Corporation
• Original Assignee: Adaptec Incorporated (Steel Partners Holdings LP)
• Inventors: Grummon, Jeffrey L., Franklin, Chris R.
• Primary Examiner(s): Ellis, Kevin L.
• Application Number:
  US09/465,354
• Time in Patent Office: 768 Days
• Field of Search: 711/161, 711/162, 711/167, 714/2
• US Class Current: 711/162
• CPC Class Codes: G06F 11/1466 to make the backup process non-disruptive
• CPC Class Codes: G06F 2201/84 Using snapshots, i.e. a logical point-in-time copy of the data
• CPC Class Codes: G06F 3/0617 in relation to availability
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD

Abstract

A system and method for enabling a snapshot container generated in a copy-on-write backup process to function in the presence of a data-handling system (e.g. a file system) that writes data to the backup disk is provided. The snapshot container, which is read-by and written-to by the system backup application is configured as a read-write container with associated driver. The write data from the backup application is provided to, and stored in the snapshot information container that also receives and stores data from the original read-write container in the manner of a backing store container. Data in the snapshot information container is selectively mapped container as a source, or to backup information container as a source, denoting a backup application write, based upon a bit-map associated with the snapshot driver arrangement. The bit-map designates discrete memory storage block within the container as being mapped to either the original read-write container or as backup write data, denoted as originating within the snapshot information container via the snapshot/backup application.

Claims

1. A system for backup of data employing a snapshot based upon a copy-on-write process in the presence of a data-handling system having a backup application arranged to provide write data to a backup disk, the system comprising:

an original read-write container;

a snapshotted container that receives write data from and provides read data to the data-handling system based upon accessing of the original read-write container by an application;

a read-write snapshot container that stores a real-time copy of data contained in the snapshotted container, data residing on the snapshot container being read by the backup application and the snapshot container being written-to by the backup application at predetermined times with the write data thereof;

a snapshot information container that stores data from the original read-write data and that stores write data of the backup application received from the snapshot container; and

a bit-map associated with the snapshot information container that maps data storage blocks therein as associated with either of the original read-write container or the write data of the backup application.

2. The system as set forth in claim 1 wherein at least one of the data storage blocks includes data associated with each of the original read-write container and the write data of the backup application, the bit map representing the one of the data storage blocks as mapped to snapshot information container as a respective source of the data.

3. The system as set forth in claim 2 wherein the original read-write container is a hidden container and the snapshotted container is arranged to transfer data therein to the original read-write container in response to an input/output (I/O) operation performed thereto.

4. The system as set forth in claim 3 wherein the snapshot information container is arranged to receive data currently stored in the original read-write container prior to transfer of data from the snapshotted container to the original read-write container in response to the I/O operation so as to preserve the data currently stored in the original read-write container in the snapshot information container.

5. The system as set forth in claim 1 wherein the data-handling system comprises a file system.

6. A method for backup of data employing a snapshot based upon a copy-on-write process in the presence of a data-handling system having a backup application arranged to provide write data to a backup disk, the system comprising:

providing an original read-write container;

receiving, at a snapshotted container, write data from and providing, from the snapshotted container, read data to the data-handling system based upon accessing of the original read-write container by an application;

storing, in a read-write snapshot container, a real-time copy of data contained in the snapshotted container, data residing on the snapshot container being read by the backup application and the snapshot container being written-to by the backup application at predetermined times with the write data thereof;

storing, in a snapshot information container, data from the original read-write data and write data of the backup application received from the snapshot container; and

mapping, with a bit-map associated with the snapshot information container, data storage blocks therein as associated with either of the original read-write container or the write data of the backup application.

7. The method as set forth in claim 6 further comprising defining at least one of the data storage blocks to include data associated with each of the original read-write container and the write data of the backup application, the bit map representing the one of the data storage blocks as mapped to snapshot information container as a respective source of the data.

8. The method as set forth in claim 7 further comprising establishing the original read-write container is a hidden container and configuring the snapshotted to transfer data therein to the original read-write container in response to an input/output (I/O) operation performed thereto.

9. The method as set forth in claim 8 further comprising configuring the snapshot information container to receive data currently stored in the original read-write container prior to transfer of data from the snapshotted container to the original read-write container in response to the I/O operation so as to preserve the data currently stored in the original read-write container in the snapshot information container.

10. The method as set forth in claim 6 wherein the steps of receiving, at a snapshotted container, write data from and providing, from the snapshotted container, read data to the data-handling system includes receiving, at a snapshotted container, write data from and providing, from the snapshotted container, read data to a file system.