Coalesced Multi-Block Read for Storage Systems
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Solution Overview
Problem
Conventional storage systems face performance issues due to non-sequential volume block numbers (VBNs) in multi-block read requests, leading to increased overhead and reduced efficiency, as they require multiple small read commands, which can be time-consuming and inefficient.
Innovation Solution
The method involves coalescing non-sequential VBNs into chains of sequential numbers, allowing for fewer, longer read commands to be transmitted asynchronously to the storage subsystem, thereby reducing the number of messages and improving system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple small read commands are issued to retrieve non-sequential VBNs, then data retrieval is possible, but system overhead increases and performance decreases
Solution Approach 1:
The patent merges multiple small read commands into a single large read command by coalescing non-sequential VBN lists into sequential ranges. The file system identifies contiguous VBN ranges that can be read in a single command, combining multiple scattered read operations into fewer, larger operations that reduce overhead and improve performance.
2Productivity
If defragmentation is performed to make VBNs sequential, then read performance improves, but disk access is blocked for a prohibitive length of time
Solution Approach 1:
The patent segments the VBN list into multiple contiguous ranges that can be read in parallel. Instead of performing a single time-consuming defragmentation operation, the file system divides the non-sequential VBNs into several sequential ranges and issues multiple read commands simultaneously, achieving performance improvement without blocking disk access for an extended period.
3Reliability
If multiple read commands are issued for non-sequential VBNs, then all required data blocks are retrieved, but the number of messages increases and overhead increases
Solution Approach 1:
The patent combines multiple small read commands into fewer, larger read commands by coalescing non-sequential VBNs into contiguous ranges. This merging approach ensures all required data blocks are retrieved while significantly reducing the number of messages and associated overhead between the file system and storage subsystem.
Data Source
AI summary
A storage system, such as a storage server, receives a list of volume block numbers (VBNs) in a multi-block read request. In response to the request, the storage system coalesces the list into one or more chains of sequential VBNs. The storage system issues each chain to the storage subsystem.