Storage Developer Conference

Successive generations of storage solutions have increased decentralization. Early NAS systems made all the decisions on a single server, down to sector assignment. Federated NAS enabled dynamic distribution of the namespace across multiple storage serves. The first Object Clusters delegated CRUD-based management of both object metadata and data to OSDs.

Current generation of Object Clusters uses Consistent Hashing to eliminate the need for central metadata. However, Consistent Hashing and its derivatives, combined with the prevalent use of TCP/IP in storage clusters results in performance hot spots and bottlenecks, diminished scale-out capability and dis-balances in resource utilization.

These shortcomings will be demonstrated with a simulation of a large storage cluster. An alternative next generation strategy that simultaneously optimizes available IOPS "budget" of the back-end storage, storage capacity, and network utilization will be explained. Practically unlimited load-balanced scale-out capability using Layer 5 (Replicast) protocol for Multicast Replication within the cluster will be presented.

Learning Objectives

Why neither Consistent Hashing nor TCP/IP scale
How CCOW (Cloud Copy-on-Write) and Replicast provide for infinite scale-out
Impact on IOPS, Storage Capacity and Network utilization
Simulation: queuing and congestion in a 4000 node cluster Actual
Results: measured with a more affordable cluster