RAID Virtual Disk Stripe Expansion With Hardware OCE Automation
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Solution Overview
Problem
Existing RAID storage systems face inefficiencies and performance penalties during online capacity expansion (OCE) due to reliance on firmware for managing IO operations, which are slower than hardware and introduce bottlenecks, leading to degraded user experience and temporary limitations.
Innovation Solution
Shift operational load from firmware to hardware by automating OCE operations at the stripe level, allowing hardware to perform read and write operations more efficiently, and use watermarking techniques to manage maintenance regions, enabling simultaneous execution of host IOs on unaffected parts of the virtual disk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If firmware controls IO operations during OCE, then maintenance operations can be performed, but performance is degraded due to firmware being slower than hardware
Solution Approach 1:
A hardware maintenance region indicator register is introduced as an intermediary between the firmware and the hardware IO execution unit. This register allows the firmware to communicate maintenance region information to the hardware without requiring the hardware to execute firmware instructions, enabling parallel hardware execution of non-conflicting IO operations while maintaining correctness through the intermediary's coordination
Solution Approach 2:
The patent replaces firmware-based IO scheduling and execution with a hardware-based system that autonomously determines whether IO operations conflict with maintenance regions. The hardware directly reads the maintenance region indicator register and makes decisions about IO execution, substituting the slower firmware mechanical process with faster hardware logic
2Reliability
If all host IOs are diverted to firmware during OCE, then data corruption is prevented, but substantial inefficiencies occur because firmware operates much more slowly than hardware
Solution Approach 1:
Instead of diverting all host IOs to firmware, the patent implements partial diversion where only IO operations that would access maintenance regions are diverted. The hardware autonomously evaluates each IO against the maintenance region indicator register and executes non-conflicting IOs directly, applying partial action only where necessary to prevent data corruption
Solution Approach 2:
The hardware system serves itself by autonomously determining whether host IO operations conflict with maintenance regions and making execution decisions without firmware intervention. The hardware reads the maintenance region indicator register and independently decides whether to execute or divert each IO, enabling self-service operation that eliminates firmware bottlenecks for non-conflicting operations
3Extent of automation
If firmware manages the entire OCE process, then detailed control is achieved, but the process becomes complex and slower
Solution Approach 1:
The patent segments the OCE control functionality into distinct components: the firmware sets maintenance region boundaries in the indicator register, the hardware autonomously manages IO execution decisions, and the maintenance operation progresses through defined phases. This segmentation separates detailed control logic from execution control, reducing firmware complexity while maintaining detailed operational control
Data Source
AI summary
Solutions for managing RAID logical devices. Some solutions provide enhanced online capacity expansion for virtual disks on RAID drives, for example by taking advantage of the hardware capabilities to expand a virtual disk stripe by stripe. Some solutions provide increase hardware automation, which can reduce firmware load and/or provide more efficient input-output operations (IO) for the online capacity expansion operation.