Virtual Storage Server High Availability via Proxy Routing
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Solution Overview
Problem
Implementing high availability (HA) in network storage systems becomes challenging when using virtual storage servers with shared-nothing storage environments, as existing HA mechanisms rely on shared storage access between redundant servers, which is difficult with direct-attached storage (DAS).
Innovation Solution
The solution involves using a proxy to route requests between storage servers logically below the RAID layer for inter-host replication and distributing storage devices across hosts, allowing existing HA mechanisms to function unmodified, with a third host providing DAS storage to both servers, enabling HA capability without requiring software modifications or additional external software.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shared storage is used for HA capability, then reliability is improved, but device complexity increases due to storage sharing requirements
Solution Approach 1:
A proxy is introduced as an intermediary component that mediates storage access between storage servers in a shared-nothing environment. The proxy enables HA capability by facilitating request routing and storage access without requiring direct storage sharing between servers, thus resolving the contradiction by maintaining reliability while avoiding complex sharing mechanisms
Solution Approach 2:
The patent replaces traditional mechanical storage sharing mechanisms with a software-based proxy system that operates logically below the RAID layer. This substitution eliminates the need for physical or logical storage sharing while achieving HA capability through request proxying, thereby reducing device complexity
2Ease of operation
If DAS storage is used instead of shared storage, then ease of operation is improved, but reliability deteriorates due to inability to access another server's storage
Solution Approach 1:
The proxy serves as an intermediary that enables DAS storage servers to access each other's storage through request proxying. This allows storage servers to maintain simple direct-attached storage operations while achieving high availability capability, as the proxy facilitates the necessary inter-server storage access without complicating the DAS architecture
Solution Approach 2:
The storage access function is segmented into separate components: local DAS storage for simplicity and a proxy layer for HA capability. This segmentation allows each component to optimize for its specific function while working together, resolving the contradiction between operational simplicity and reliability
3Reliability
If HA mechanisms are modified to work with DAS, then reliability is improved, but device complexity increases due to software modifications
Solution Approach 1:
Rather than modifying HA mechanisms to work with DAS, the patent introduces a proxy as an intermediary that enables existing HA mechanisms to function unmodified in a DAS environment. The proxy handles the complexity of DAS storage access, allowing traditional HA mechanisms to operate as before, thus improving reliability without increasing complexity
Solution Approach 2:
Instead of modifying HA mechanisms to accommodate DAS, the patent inverts the approach by making the HA mechanism the constant and introducing the proxy to adapt to DAS storage. This inversion eliminates the need for HA mechanism modifications while achieving reliability in a DAS environment
Data Source
AI summary
A technique is disclosed for providing high availability (HA) capability with a plurality of storage servers, which may be virtual storage servers (VSSs), in a shared-nothing storage environment. The technique uses a proxy mechanism to route requests originating at one storage server to an HA partner storage server, where the proxy is implemented inside a VSS logically below the RAID layer. The technique also involves distributing non-shared storage devices “owned” by a storage server so that existing storage device-based heartbeat and fencing mechanisms can function unmodified for HA VSSs in shared-nothing environments. For example, a third, external host can be used to provide and export its non-shared storage to first and second storage servers, where the first and second storage servers do not own the non-shared storage on their local physical host machine.