Mirrored Storage Buddy Retention for Rapid Recovery
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Solution Overview
Problem
During staggered downtime for maintenance, mirrored data on a storage device becomes out-of-date, and existing methods for resynchronization are inefficient, leading to potential data loss and prolonged recovery times.
Innovation Solution
The implementation of a 'no-loss rapid recovery' mechanism, which involves a two-stage process: the 'buddy-retention stage' where writes are redirected to a retention buddy's non-volatile cache and primary storage, and the 'rapid resynchronization stage' where only tracked changes are used to bring the offline buddy up-to-date, minimizing data loss and accelerating recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is mirrored on multiple storage devices and one device is taken down for maintenance, then data availability is maintained through staggered downtime, but the resynchronization process becomes time-consuming and may result in data loss
Solution Approach 1:
The patent applies preliminary action by maintaining a retention buddy that proactively holds copies of data blocks before they are needed for resynchronization. When a storage device is taken offline, the retention buddy already has the current data blocks ready, eliminating the need for time-consuming resynchronization operations during the recovery phase.
Solution Approach 2:
The retention buddy acts as an intermediary between the offline storage device and the online mirror buddies. It receives and holds data blocks during the offline period, then provides them during resynchronization, mediating the data transfer process and reducing the burden on other mirror buddies while accelerating recovery.
2Reliability
If all mirrored data is resynchronized from primary storage, then data consistency is ensured, but the resynchronization process is slow and inefficient
Solution Approach 1:
The patent extracts only the necessary data blocks for resynchronization from the set of all mirrored data. The retention buddy identifies and holds only the specific data blocks that need to be synchronized, rather than transferring all mirrored data. This selective approach maintains data consistency while dramatically improving resynchronization speed.
Solution Approach 2:
The resynchronization process is segmented into identifying only the specific data blocks that require synchronization, rather than treating all mirrored data as a single unit. The retention buddy manages individual data blocks independently, allowing selective transfer and significantly reducing the overall resynchronization time while ensuring consistency for the necessary blocks.
3Quantity of substance
If data is stored only in primary storage, then storage capacity is maximized, but data retrieval and resynchronization speeds are reduced
Solution Approach 1:
The patent applies local quality by creating a specialized high-speed storage region (the retention buddy) with different properties than primary storage. The retention buddy uses faster storage media to hold copies of frequently accessed or recently modified data blocks, providing rapid data retrieval for resynchronization operations while primary storage maintains overall storage capacity.
Solution Approach 2:
The retention buddy is nested within the storage system architecture as a layered structure. It sits between the client and primary storage, holding a subset of data blocks in a high-speed medium. This nested arrangement provides fast access to critical data while primary storage maintains the bulk storage capacity, creating a hierarchical storage system.
Data Source
AI summary
No-loss rapid recovery performs resynchronization efficiently while concurrently allowing availability to mirrored data on the storage device. No-loss rapid recovery has two stages and involves storage devices that have both a non-volatile cache and primary storage and that operate as mirror buddies. The first stage is referred to herein as the buddy-retention stage. During the buddy-retention stage, writes to mirrored data are not performed on the offline mirror buddy but are performed on the online mirror buddy. The mirrored data changed in the online mirrored buddy is retained in the non-volatile cache of the retention buddy. The next stage is referred to herein as the rapid resynchronization stage. In this stage, the changed mirrored data retained by the retention buddy for no-loss rapid recovery is used to resynchronize the offline buddy. The storage device is resynchronized using the changed mirrored data retained in the cache of the mirror buddy.