Combined Data and Checksum Block I/O for Lower Storage Latency
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Solution Overview
Problem
Existing storage stack systems incur increased latency due to separate processing of data block and checksum block I/O operations, leading to inefficiencies and prolonged round trip times in communicating with underlying storage device layers.
Innovation Solution
The file system layer combines data block and checksum block I/O operations into a single I/O operation, and the storage layer accumulates multiple I/O operations into a single combined operation, reducing latency by minimizing separate processing and round trip times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data block I/O and checksum block I/O are processed separately, then data integrity validation can be performed, but I/O processing latency increases and round trip time is prolonged
Solution Approach 1:
The patent combines data block I/O operations and checksum block I/O operations into a single unified I/O operation. The storage stack receives a first I/O operation for data blocks and a second I/O operation for checksum blocks, then merges these into a single combined operation that retrieves both data and checksums simultaneously from the underlying storage device, eliminating sequential round trips and reducing latency while maintaining integrity validation capability
Solution Approach 2:
The system performs preliminary actions by pre-calculating and storing checksums with data blocks during the write operation. When read operations are needed, the checksums are already available alongside the data blocks, allowing immediate validation without requiring separate sequential I/O operations to fetch checksums afterward
2Device complexity
If separate I/O operations are used for data blocks and checksum blocks, then processing can be simplified, but I/O operations per second decreases
Solution Approach 1:
The storage stack merges multiple I/O operations into a single combined operation that targets both data blocks and checksum blocks simultaneously. This consolidation increases I/O operations per second by reducing the total number of separate operations the stack must process, while the internal structure remains organized enough to maintain processing simplicity through systematic combination of related operations
3Ease of operation
If multiple I/O operations are processed sequentially, then each operation can be handled independently, but CPU and memory usage increases
Solution Approach 1:
The patent combines multiple I/O operations into a single operation that retrieves both data blocks and their corresponding checksums in one sequential access pattern. This reduces the total number of times the CPU must context-switch between operations and minimizes memory bandwidth consumption by consolidating sequential reads into a single efficient operation, while maintaining independent handling capability through structured operation combination
Data Source
AI summary
Techniques are provided for combining data block and checksum block I/O into a single I/O operation. Many storage systems utilize checksums to verify the integrity of data blocks stored within storage devices managed by a storage stack. However, when a storage system reads a data block from a storage device, a corresponding checksum must also be read to verify integrity of the data in the data block. This results in increased latency because two read operations are being processed through the storage stack and are being executed upon the storage device. To reduce this latency and improve I/O operations per second, a single combined I/O operation corresponding to a contiguous range of blocks including the data block and the checksum block is processed through the storage stack instead of two separate I/O operations. Additionally, I/O operation may be combined into a single request that is executed upon the storage device.