Storage Pool Allocator Dynamic Block Reallocation
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Solution Overview
Problem
In computer systems, when a disk in a storage pool becomes offline, the file system lacks the ability to select an alternate location for data writing, leading to failed write operations due to its reliance on a logical representation of storage and lack of awareness about fault domains.
Innovation Solution
A system and method that includes a storage pool allocator (SPA) which receives requests to write logical blocks, allocates physical blocks on one disk, and if the write to that disk fails, allocates an alternate physical block on another disk in the storage pool, ensuring data integrity and availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the file system uses a logical representation of storage and relies on block allocation map for tracking physical blocks, then the file system can manage storage efficiently and maintain abstraction, but the file system loses the ability to detect disk failures and select alternate locations when a disk goes offline
Solution Approach 1:
The patent introduces a volume manager as an intermediary layer between the file system and the physical storage devices. The volume manager receives write requests from the file system, translates logical block addresses to physical disk locations, and handles fault detection and alternate location selection. This intermediary maintains the abstraction benefits while adding the capability to detect disk failures and redirect writes to healthy disks.
Solution Approach 2:
The patent segments the storage management functionality into distinct components: the file system maintains the block allocation map for logical tracking, while the volume manager handles physical block allocation, fault detection, and alternate location selection. This segmentation allows each component to specialize in its function, with the volume manager having access to both the block allocation map and disk status information to make intelligent routing decisions.
2Loss of information
If the file system tracks physical block allocation through a block allocation map, then the file system can monitor free blocks for allocation, but the file system cannot determine which specific disks are offline or available for writing
Solution Approach 1:
The patent merges the block allocation map information with disk status information in the volume manager. The volume manager maintains knowledge of both which blocks are allocated/free and which disks are online/offline. When a write request arrives, the volume manager combines this information to select a healthy disk that has available blocks, ensuring both block availability and fault domain awareness.
3Reliability
If a disk in the storage pool goes offline, then the system must maintain data availability, but the file system lacks the capability to redirect writes to alternate disks
Solution Approach 1:
The patent implements dynamic block allocation where the volume manager can adaptively select different physical disks for writing based on real-time disk availability. When a disk goes offline, the volume manager dynamically redirects write requests to alternate healthy disks, selecting from available blocks on those disks. This dynamic adaptation maintains data availability without requiring file system changes.
Data Source
AI summary
A system includes a storage pool including a first disk and a second disk, a data management unit (DMU), and a storage pool allocator (SPA). The SPA is configured to receive a request from the DMU to write a logical block, allocate a first physical block on the first disk, attempt to write the logical block to the first physical block, and allocate a second physical block on the second disk, if the attempt to write the logical block to the first physical block fails.