Abstract: An apparatus in one embodiment comprises a storage system including a plurality of storage nodes each associated with one or more storage devices. The storage system is configured to provide at least one virtual volume distributed over the storage nodes for utilization by a plurality of host devices. The storage nodes comprise respective input-output sequencers for handling input-output operations directed to the distributed virtual volume by the host devices. The input-output sequencers of the respective storage nodes are configured to interact with one another to collectively form a distributed input-output sequencer that ensures consistency across the storage nodes for the distributed virtual volume when accessed by different ones of the host devices. The storage system may comprise a multi-site storage system, with the plurality of storage nodes comprising at least a first storage node cluster at a first site and a second storage node cluster at a second site.

Abstract: An apparatus in one embodiment comprises a storage system including a plurality of storage nodes each associated with one or more storage devices. The storage system is configured to provide at least one virtual volume distributed over the storage nodes for utilization by a plurality of host devices. The storage nodes are configured to support selection between multiple operating modes for handling input-output operations directed to the distributed virtual volume by the host devices. The multiple operating modes comprise at least a cached mode of operation in which consistency across the storage nodes for the distributed virtual volume when accessed by different ones of the host devices is ensured utilizing a distributed cache coherence protocol implemented by cooperative interaction of cache controllers of respective ones of the storage nodes, and a cacheless mode of operation in which consistency is ensured without utilizing the distributed cache coherence protocol and its associated cache controllers.

Abstract: A share group for a distributed volume is separated into two non-overlapping, cluster-local SGCs (share group cliques). Each SGC has an independent local meta-directory master hosted by a computing node of the SGC cluster. Each SGC maintains an independent local directory for the distributed volume. The directory may be spread across multiple computing nodes of the SGC cluster. Changes to the distributed volume (writes) are coordinated across the pair of SGCs to provide data consistency. The coordination of these changes is conducted using relatively few inter-SGC round-trips. Read access to the distributed volume is safely conducted without inter-SGC coordination.