Witness Sled Failover for High-Availability Chassis Storage
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Solution Overview
Problem
Existing virtualized storage area networks (vSANs) in edge computing environments face data inconsistency issues due to redundant data mirroring across multiple storage resources, which can lead to fault tolerance challenges.
Innovation Solution
A chassis with a primary witness sled and a chassis management controller that arbitrates data discrepancies by maintaining a copy of witness transactions, selecting a failover witness sled, and migrating operations to ensure high-availability data storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is mirrored across multiple storage resources for fault tolerance, then reliability is improved, but data inconsistency issues arise
Solution Approach 1:
The patent introduces a witness sled as an intermediary component that maintains a copy of metadata and arbitration capabilities. This witness sled acts as a mediator to resolve data inconsistency between mirrored storage resources by providing a trusted reference point for determining which copy is authoritative, thus preventing information loss while maintaining reliability
Solution Approach 2:
The patent creates a copy of the witness sled's metadata and arbitration state on a secondary witness sled. This copying mechanism ensures that if the primary witness sled fails, the secondary can take over without losing the arbitration capability, thereby maintaining data consistency while preserving the fault tolerance provided by mirroring
2Loss of information
If a primary witness sled is used to arbitrate data discrepancies, then data consistency is improved, but single point of failure risk increases
Solution Approach 1:
The patent pre-configures a secondary witness sled with a copy of the arbitration metadata and state before the primary witness sled fails. This preliminary action ensures that when the primary witness sled becomes unavailable, the secondary can immediately take over without interruption to data consistency arbitration, thus eliminating the single point of failure while maintaining data consistency
Solution Approach 2:
The patent implements dynamic failover where the operational state parameter of the witness sled changes from primary to secondary based on detected failure conditions. This parameter change allows the system to transition from a single active witness to a standby witness configuration, maintaining availability while preserving the arbitration capability for data consistency
3Productivity
If witness operations are centralized in a single sled, then arbitration efficiency is improved, but operational continuity is compromised when the sled fails
Solution Approach 1:
The patent pre-replicates the witness metadata and arbitration state to a secondary sled before failure occurs. This preliminary replication ensures that when the primary witness sled fails, the secondary can immediately assume the arbitration function without loss of efficiency, thus maintaining both arbitration productivity and operational continuity
Solution Approach 2:
The patent implements a dynamic witness configuration where the system can transition from a single active witness sled to a standby witness sled based on operational conditions. This dynamic behavior allows the system to maintain centralized arbitration efficiency when the primary is operational while ensuring operational continuity through automatic failover to the secondary witness when needed
Data Source
AI summary
Systems and methods provide failover operations for witness sled hardware installed in a chassis. The chassis may include data storage devices and Information Handling Systems (IHSs), each storing data redundantly to the storage devices, such as in a vSAN. A primary witness sled provides witness functions, such as arbitrating discrepancies in the redundantly stored data. The chassis includes a chassis management controller (CMC) that connects with the primary witness sled via a management signaling pathway and maintains a copy of witness transactions stored by the primary witness sled based on transactions transmitted via the management signaling pathway. The CMC generates an inventory of co-located witness sleds. Upon detecting the primary witness sled is not operational, the CMC selects a failover witness sled from the inventory of co-located witness sleds and migrates witness operations of the primary witness sled to the selected failover witness sled.