Caching Mapping Information for Off-Host Backup Clients
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Solution Overview
Problem
Traditional off-host backup methods still require significant client processing, which can be time-consuming and disrupt services, necessitating further reduction in backup overhead for backup clients.
Innovation Solution
Implementing a method that caches extent information for off-host backups, where unrelocated data blocks reuse previously calculated mapping information, and relocated blocks recalculate mapping information, reducing the need for extensive client processing by providing the media server with either cached or recalculated mapping information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If off-host backup is implemented to move processing from backup client to media server, then backup client processing time is reduced, but some client processing overhead remains necessary
Solution Approach 1:
The system performs preliminary actions by caching mapping information from previous backup operations. The backup client stores mapping information that maps client file system blocks to storage device blocks, so that in subsequent backups, this pre-computed information can be reused without requiring recalculation, thereby reducing processing overhead while maintaining backup functionality
Solution Approach 2:
The system creates and stores a copy of mapping information from previous backup operations. Instead of recalculating mapping relationships during each backup, the system retrieves and uses the cached copy of mapping information, significantly reducing the processing burden on the backup client while enabling off-host backup operations
2Reliability
If mapping information is recalculated for all blocks during each backup, then backup accuracy is maintained, but backup window time increases
Solution Approach 1:
Instead of recalculating mapping information for all blocks during each backup operation, the system performs partial recalculation only for blocks that have changed since the last backup. The system compares current block locations with cached mapping information and recalculates only when necessary, maintaining backup accuracy while significantly reducing the time required
Solution Approach 2:
The system implements a feedback mechanism where mapping information is cached from previous operations and reused in subsequent operations. The system checks whether mapping information has changed and only recalculates when feedback indicates changes have occurred, thereby maintaining reliability while minimizing redundant processing time
3Reliability
If backup client processes more data locally, then backup completeness improves, but client service availability decreases
Solution Approach 1:
The system extracts the mapping information generation and caching function from the backup client's real-time processing duties. By moving mapping information caching to a separate, pre-computed process that runs independently of active client services, the system ensures backup completeness through thorough mapping information collection while minimizing disruption to client service availability
Data Source
AI summary
Various systems and methods cache extent information for use in off-host backups. One method involves detecting that a first set of one or more blocks of client data has not been relocated subsequent to a prior off-host backup operation while also detecting that a second set of one or more blocks of the client data has been relocated subsequent to the prior off-host backup operation. In response to detecting that the first set has not been relocated, the method provides a media server with a previously calculated set of mapping information for the first set instead of recalculating that mapping information. In contrast, in response to detecting that the second set has been relocated subsequent to the prior off-host backup, the method recalculates mapping information for the second set. The media server is provided with the recalculated mapping information instead of previously calculated mapping information for the second set.