Data Storage Device Recovery Read Command Segmentation
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Solution Overview
Problem
In data storage systems, especially those using rotating media-based hard drives, the transfer of data from a failing storage device to a replacement device is time-consuming and resource-intensive due to the need to access both cache and storage portions, leading to potential complete failure of the failing device and increased access delays.
Innovation Solution
Implementing a system where data storage devices respond to recovery read commands by retrieving data only from the storage portion and not the cache portion, and transferring this data to a replacement device, while also providing cache block lists to the host system for retrieval of cached data, thereby avoiding seek penalties and access delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is transferred from both cache portion and storage portion of a failing data storage device to a replacement device, then complete data recovery is achieved, but access time increases and the device is at higher risk of complete failure
Solution Approach 1:
The patent segments the data retrieval process into two distinct phases: first retrieving data from the storage portion only during the critical recovery transfer, then separately handling cache data afterward. This segmentation allows the urgent recovery operation to focus only on persistent storage data, avoiding the time-consuming cache access while still achieving complete data recovery eventually.
Solution Approach 2:
The patent applies preliminary action by first transferring data from the storage portion before attempting to access cache data. This preliminary transfer ensures that the most critical data (from non-volatile storage) is recovered first, minimizing the window of vulnerability and reducing overall access time while maintaining complete data recovery.
2Reliability
If data is accessed from both cache portion and storage portion on the same rotating media, then complete data recovery is achieved, but seek penalties and access delays increase
Solution Approach 1:
The patent segments the data source into storage portion and cache portion, retrieving data from storage portion first without accessing cache. This segmentation eliminates the need for seek operations between different regions on the rotating media during the critical recovery phase, thereby eliminating seek penalties and improving data transfer speed while still achieving complete data recovery.
3Loss of information
If the failing data storage device is accessed extensively during data transfer, then complete data can be recovered, but the device is at higher risk of complete failure
Solution Approach 1:
The patent applies partial action by retrieving only the necessary data from the storage portion during the critical recovery window, without attempting to access cache data from the same vulnerable device. This partial retrieval approach recovers the essential data while minimizing the extent of access to the failing device, thereby reducing stress and the risk of complete failure during the recovery process.
Data Source
AI summary
Systems, methods, and firmware for recovery of data from storage devices are provided herein. In one example, a data storage device is provided. The data storage device includes a storage portion and a cache portion which caches data intended for storage in the storage portion. Responsive to a recovery read command identifying requested data, the data storage device retrieves stored data corresponding to the requested data from the storage portion without retrieving cached data corresponding to the requested data from the cache portion that supersedes at least a portion of the stored data. Responsive to a cache block list command, the data storage device transfers a list identifying one or more cached blocks of the cached data. Responsive to a read command that identifies at least one cached block, the data storage device retrieves the at least one cached block.