Out-of-Order Dirty Block Transfer for Backup Overhead Reduction
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Solution Overview
Problem
Incremental data backup processes in data storage systems face inefficiencies due to high overheads from copy-on-write operations, which incur additional I/O operations and storage space usage, especially when handling dirty blocks during concurrent read and write operations.
Innovation Solution
Implementing a method where dirty blocks are identified and transferred based on their access patterns and priority, with copy-on-write or redirect-on-write operations only triggered for blocks that need data integrity preservation, and using a transfer order different from sequential logical order to optimize data content preservation and reduce overheads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copy-on-write operations are performed to ensure data integrity during backup, then data reliability is improved, but I/O overhead and storage space usage increase
Solution Approach 1:
The patent applies local quality by differentiating between dirty blocks (modified data) and clean blocks (unmodified data). Copy-on-write operations are performed selectively only for dirty blocks that require data integrity preservation, while clean blocks are transferred without additional copy operations. This localized approach maintains reliability where needed while minimizing I/O overhead in areas where it is not required.
Solution Approach 2:
The patent implements partial action by performing copy-on-write operations on only a subset of blocks (dirty blocks) rather than all blocks during backup. The system identifies modified blocks through change tracking mechanisms and applies data preservation operations only to those specific blocks, avoiding excessive copy operations on unchanged data and thereby reducing overall I/O overhead.
2Ease of operation
If sequential logical order transfer is used for simplicity, then ease of operation is improved, but transfer overhead and time increase
Solution Approach 1:
The patent applies dynamics by making the block transfer order adaptive rather than fixed. The system dynamically determines transfer order based on block priorities, access patterns, and dirty block identification. High-priority dirty blocks are transferred first, while low-priority or clean blocks may be deferred or batched, creating a flexible transfer sequence that optimizes backup duration without sacrificing operational simplicity.
Solution Approach 2:
The patent implements preliminary action by pre-identifying dirty blocks and determining their transfer priority before the actual transfer process begins. Change tracking mechanisms record which blocks have been modified, and transfer ordering is predetermined based on this information. This preliminary classification allows the system to optimize transfer sequences in advance, reducing actual transfer time during the backup operation.
Data Source
AI summary
Techniques for reducing overheads of primary storage transferring during a backup by transferring in an out-of-order manner are described herein. According to one embodiment, in response to a request at a primary storage for a backup of a plurality of data blocks, a transfer order of dirty data blocks is determined based on an access assessment of the dirty data blocks, wherein the dirty data blocks are data blocks of the plurality of data blocks that have been changed from a previous backup, and wherein the transfer order is different from a sequential logical order of the dirty data blocks provided by the primary storage. Then the dirty data blocks are transferred to a secondary storage in the determined order.