Interdisk

Interdisk is a formalized cross-disk coordination protocol and software abstraction designed to coordinate data placement and access across multiple storage devices within an array. It aims to treat a collection of disks as a single, coherent storage pool while preserving independence of individual disks. Interdisk specifies interfaces for metadata, data movement, and fault management that are implemented by storage controllers and client software.

Origins and development: Interdisk emerged in the mid-2010s through a collaboration of storage vendors, researchers, and standardization bodies seeking to improve scalability for large disk farms and to enable more flexible data layouts than traditional RAID can provide. The standard matured through successive revisions to address metadata locality, access scheduling, and failure handling.

Architecture: The architecture comprises three layers: a metadata layer that tracks mapping of logical to physical blocks, a distributed inter-disk bus that carries control and data commands, and a set of host-side libraries that implement Interdisk protocols. A central or distributed metadata service coordinates rebalancing and failure recovery, while disks expose a common, standardized interface for commands such as read, write, migrate, and repair.

Key features: Dynamic data placement and rebalancing based on workload, fault tolerance through parity or replication schemes, efficient hot-swapping and rebuild, and compatibility with existing storage interfaces to ease integration. Interdisk also supports snapshotting and lightweight transactions across disks.

Usage and reception: In pilot deployments, Interdisk has been used to increase throughput in large arrays and to simplify maintenance of heterogeneous disk pools. Adoption remains limited due to complexity, vendor fragmentation, and the inertia of established storage protocols, though it continues to influence research and some vendor offerings in hybrid storage environments.

See also: Storage area network, RAID, distributed file systems.