Zoned Namespace SSD RAID Mapping for Ordered High-Queue-Depth Writes
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Solution Overview
Problem
Existing RAID systems with zoned namespaces SSDs face performance issues due to the inability to support high queue-depth writes, leading to reordered logical block addresses and impaired XOR operations for data recovery upon drive failure.
Innovation Solution
Implementing a stripe mapping table and a logical-to-physical mapping table in the host system to manage parity and data strip alignments, ensuring write operations are performed with queue-depth 1 and maintaining strip correspondence, while using a RAID controller to manage stripe mappings and rebuild processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high queue-depth writes are used on zoned namespaces SSDs, then write throughput is improved, but logical block address reordering occurs which impairs XOR operations for data recovery
Solution Approach 1:
The patent implements preliminary ordering of write operations at the host system level before data is sent to the zoned namespaces SSDs. The host system tracks logical block addresses and ensures they are written in sequential order, preventing reordering issues that would occur with high queue-depth writes. This preliminary action maintains the reliability of XOR operations while still allowing high throughput by using multiple ordered write streams.
Solution Approach 2:
The patent introduces an intermediary layer (the host system's RAID controller and mapping tables) between the host and the zoned namespaces SSDs. This intermediary tracks logical-to-physical address mappings and ensures proper ordering of writes, acting as a mediator that allows high queue-depth writes to proceed while maintaining the necessary order for reliable data recovery through XOR operations.
2Reliability
If queue-depth 1 writes are enforced to maintain strip alignment, then data recovery reliability is improved, but write performance is degraded
Solution Approach 1:
The patent segments the write operations into multiple independent streams or channels, each operating at queue-depth 1 to maintain proper strip alignment. By dividing the write workload across multiple segmented streams that each follow sequential addressing, the system achieves both reliable strip alignment for data recovery and improved overall throughput compared to a single queue-depth 1 stream.
Solution Approach 2:
The patent uses partial action by implementing queue-depth 1 enforcement only for specific critical write operations that require strict strip alignment, while allowing other operations to use higher queue depths. This selective application of the constraint maintains reliability where needed while preserving performance where possible.
Data Source
AI summary
High performance parity-based Redundant Array of Independent Disks (RAID) on Zoned Namespaces Solid State Drives (SSD)s with support for high queue depth write Input Output (IO) and Zone Append command is provided in a host system. The host system includes a stripe mapping table to store mappings between parity strips and data strips in stripes on the RAID member SSDs. The host system also includes a Logical to Physical (L2P) table to store data block addresses returned by the Zone Append command.