An Overview of EMC Elastic Cloud Storage (ECS): Architecture, Features, and Performance

EMC's Elastic Cloud Storage (ECS) is the third‑generation object storage system, succeeding Centera (2001) and Atmos (2008); since 2014 it supports the S3 protocol while retaining legacy APIs for compatibility.

The product architecture is organized into six layers: (1) the web‑based portal and provisioning service for self‑service, automation, reporting and multi‑tenant management; (2) the data service offering object, HDFS and NFSv3 interfaces; (3) the storage engine handling data storage, retrieval, transaction management and replication; (4) the fabric providing cluster health, software configuration, upgrades and alerts; (5) the infrastructure based on SUSE Linux Enterprise Server; and (6) the underlying hardware, either turnkey appliances or qualified commodity servers.

ECS supports a wide range of protocols: S3 for new users, legacy CAS and Atmos APIs, Swift, as well as HDFS and NFS. Instead of the community S3A client, ECS implements its own dedicated HDFS client, which typically yields better performance and richer functionality.

Multi‑site capabilities enable disaster‑recovery and cross‑site analytics; data protection relies on erasure coding (EC) with three‑copy metadata replication. Objects are stored in fixed 128 MiB chunks, larger than Ceph’s default 4 MiB, and indexed via a B+‑tree that allows limited custom attribute reverse look‑ups.

Write caching is currently memory‑based because ECS does not yet support SSD write cache; a forthcoming version plans to add SSD caching. Writes are double‑written to ensure durability, which can impact performance.

Data replication is asynchronous, while metadata replication is synchronous, giving clients a perception of strong consistency; however, a primary site failure can still lead to data loss. The Box‑Carting feature merges small files into 2 MiB blocks in memory before persisting them, improving write throughput.

Limitations include the absence of SSD write cache (until the next release), a simple small‑file merge strategy, lack of replica‑based protection, limited expansion and QoS controls, a minimum five‑node deployment, and containerized components without built‑in load balancing.

Future road‑map items for ECS include SSD caching, support for new hardware, full‑flash configurations, and hybrid‑cloud capabilities; the product is recognized as a leader in Gartner and IDC analyst quadrants.