Storage Shelf Router Virtual Formatting for Disk Array Delays
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Solution Overview
Problem
Current disk array systems using Fibre Channel (FC) arbitrated loops face issues such as cumulative node delays, single-point failures, complex failure identification, and limitations in interconnecting large numbers of disks due to the FC arbitrated loop topology, as well as challenges in incorporating new disk drives and enhancing error detection capabilities without re-engineering disk array controllers.
Innovation Solution
The implementation of a storage-shelf router that interconnects disk drives within a storage shelf to a high-bandwidth communications medium, providing virtual disk formatting and error correction, and using dual-abstraction methods to align virtual-block reads with underlying device blocks, while tracking and correcting corrupted device blocks during READ-MODIFY operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If FC arbitrated loop topology is used to interconnect disk drives, then data transfer can be achieved, but cumulative node delays occur and the number of interconnectable disks is limited
Solution Approach 1:
The system segments the disk array into multiple storage shelves, each independently interconnected to the FC arbitrated loop. This segmentation reduces the number of nodes on each loop, thereby reducing cumulative node delays while maintaining data transfer capabilities.
Solution Approach 2:
The patent introduces a hierarchical dimension by adding storage shelf routers that manage multiple disks per shelf. This creates a multi-level interconnection structure that bypasses the limitation of single-loop node count, enabling more disks to be interconnected without proportionally increasing loop node delays.
2Ease of operation
If FC arbitrated loop is used, then disk drives can be interconnected, but single-point failures occur and failure identification becomes complex
Solution Approach 1:
By dividing the disk array into multiple independent storage shelves connected to the FC loop, the system isolates potential failure points. A failure in one shelf does not propagate to other shelves, improving overall reliability and simplifying failure identification.
Solution Approach 2:
Storage shelf routers act as intermediaries between individual disk drives and the FC arbitrated loop. These routers provide isolation and buffering, preventing single-point failures from affecting the entire system and simplifying failure diagnosis by localizing issues to specific shelves.
3Adaptability or versatility
If traditional formatting methods are used, then disk drives can be accessed, but integrating new disk drives requires re-engineering disk array controllers
Solution Approach 1:
The storage shelf router serves as an intermediary that handles formatting and protocol translation between diverse disk drive interfaces and the FC protocol. This abstraction layer allows new disk drives to be integrated without modifying the disk array controller, as the router adapts to different drive formats.
Solution Approach 2:
The storage shelf router is designed with universal interface capabilities that support multiple disk drive formats and protocols. This multi-functionality enables the system to accommodate new disk drive technologies without requiring controller re-engineering, as the router can be configured to handle various formats.
4Reliability
If virtual formatting is implemented, then error detection capabilities can be enhanced, but additional processing overhead is introduced
Solution Approach 1:
The storage shelf router implements virtual formatting as an intermediary processing layer that enhances error detection through additional checksumming and data validation. While this introduces processing overhead, the router's dedicated hardware accelerates these operations, minimizing the impact on overall system performance.
Data Source
Figure 1A~1C
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AI summary
In various embodiments, the present invention provides virtual disk formatting by intermediate devices including: (1) a storage shelf router and the storage shelf in which the storage-shelf is included, to external computing entities, such as disk-array controllers and host computers; (2) an I/O controller; and (3) a storage-bridge device. Additional embodiments of the present invention enhance virtual formatting by using additional padding, in a dual-abstraction method, to efficiently align virtual-block reads with underlying device blocks. Yet additional embodiments of the present invention allow for tracking and correcting device blocks corrupted during READ-MODIFY operations that occur during virtual-block WRITE operations. Various intermediate devices may employ two or more of the virtual formatting, dual abstraction, and corrupted-device-block tracking methods.