pNFS-Lattice ARCHITECTURE

Architecture Overview

 

 

 

The Lattice architecture is separated into four major concerns: 

  • Protocol State Plane. The shared semantic authority for client, session, replay, lease, stateid, layout, fencing, and failover state.
  • Lattice Core. The pluggable user-space MDS runtime that executes namespace, layout, placement, and cluster-aware metadata workflows.
  • MD Catalog Authority. The authoritative, versioned metadata truth for namespace, identity, attributes, placement, reverse indexes, and workflow state. 
  • Data Server Control Plane. The DS-facing orchestration layer for the storage backbone, using direct MDS-to-DS RPC for registry, health, provisioning, placement coordination, and future persistent data services.  

Protocol State Plane

  • Role: The shared semantic authority for client, session, replay, lease state_id, and layout state. 
  • The Shift: Moves beyond isolated, per-node memory to enable safe, elastic failover and takeover
  • The Goal: State is no longer permanently tied to a single daemon process. 
  • Current: RonDB scaled-out KVS. 

 

 

 

Lattice CORE

  • Role: The pluggable user-space MDS runtime.
  • Execution: Orchestrates namespace operations, layout decisions, placement logic, and cluster-aware workflows.
  • Modularity: In Phase 1 this runs the NFSv4.2 / pNFS personality. In the future, it will act as a foundation for new distributed storage  implementations.
  • Current: Tested with 8 x MDS shards, designed for 64 x MDS plus 

 

 

 

MD Catalog Authority

  • Role: The authoritative, versioned truth for namespace, identity, attribute, placement and workflow state. 
  • The Shift: The MDS Authority is no longer trapped in a single daemon's memory. It is a shared, distributed KVS substrate. 
  •  Phase 1 - Current: Implemented using RonDB to provide a genuine shared metadata authority for multi-MDS cluster development. 

 

 

 

Data Server Control Plane

  • Role: Direct MDS-to-RPC for registry, health, and provisioning.
  • The Shift: Keeps DS-side control in the metadata plane with finer grained RPC as opposed to client-based mounts on the MDS.
  • The Benefit: Maintains loose coupling to unpatched knfsd DS targets, cleanly separating metadata authority from data-server execution. 

 

 

 

The Lattice Solution

Separation of concerns, unified at scale
  • The Monolith Problem: Legacy systems fused state, execution, and authority
  • The Lattice Solution: Cleanly separating these four planes allows Lattice to achieve what earlier systems could not: true horizontal scaling for metadata where static and ephemeral MDS instances can safely join and leave the cluster.