Persistent Reservation for Shared-Write Access in Server Clusters
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Solution Overview
Problem
Existing server cluster technologies implement a share-nothing model where only the owner node has exclusive access to shared storage devices, preventing other healthy nodes from simultaneous read and write access, which limits data accessibility and availability.
Innovation Solution
A persistent reservation mechanism that allows non-owning nodes to register shared keys with a registration table, enabling read and write access while ensuring only valid nodes maintain access, with the owner node defending ownership challenges and preempting invalid nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the owner node maintains exclusive ownership of the storage device through persistent reservation, then the reliability and data integrity are improved, but the productivity and data accessibility deteriorate because other healthy nodes cannot simultaneously write to the storage device
Solution Approach 1:
The patent segments the access rights by introducing different types of persistent reservations: exclusive reservations for the owner node and shared reservations for healthy non-owner nodes. This segmentation allows simultaneous read-write access for multiple nodes while maintaining ownership hierarchy and data integrity through the owner node's control over reservation allocation and validation.
2Productivity
If shared read-write access is granted to multiple nodes, then the productivity and data accessibility are improved, but the reliability and security worsen because invalid nodes may gain unauthorized access
Solution Approach 1:
The patent implements feedback mechanisms where the owner node continuously monitors and validates the credentials of nodes seeking shared access. The owner node receives access requests, validates node credentials against cluster membership information, and dynamically grants or revokes shared reservations based on current cluster state, ensuring that only valid healthy nodes maintain access while preventing unauthorized access by invalid nodes.
Data Source
AI summary
Described is a technology by which an owner node in a server cluster maintains ownership of a storage mechanism through a persistent reservation mechanism, while allowing non-owning nodes read and write access to the storage mechanism. An owner node writes a reservation key to a registration table associated with the storage mechanism. Non-owning nodes write a shared key that gives them read and write access. The owner node validates the shared keys against cluster membership data, and preempts (e.g., removes) any key deemed not valid. The owner node also defends ownership against challenges to ownership made by other nodes, so that another node can take over ownership if a (formerly) owning node is unable to defend, e.g., because of a failure.