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Understanding Private Cloud Storage: Page 2 of 2

Partly Cloudy

Given the attention that cloud computing garners these days, some vendors are rebranding existing offerings as private cloud options. This can be frustrating for potential buyers, but religious arguments over what constitutes a cloud are less important than features, capabilities, and cost.

Caringo and HDS have repositioned their content addressable storage (CAS) and redundant array of independent nodes (RAIN) systems as private cloud storage. There are some similarities. For instance, CAS/RAIN architectures tend to be built with less-expensive disks than you'd find in an enterprise SAN.

However, vendors have traditionally positioned CAS/RAIN architectures for archiving and compliance. Those use cases require more-advanced features than most private cloud providers offer, such as deduplication, or the ability to set retention and disposition policies or use hash algorithms to demonstrate that objects haven't been changed after they're saved. These advanced features let vendors charge a premium, which starts to push these products outside the low-cost boundary of a private cloud. In addition, the amounts of data CAS/RAIN storage systems are intended to hold are usually smaller, and have lower performance requirements, than a private cloud architecture.

Bycast StorageGrid
Software; location aware; supports multitenancy and multiple data tiers

Caringo CAStor
CAS/RAIN software; replicates among clusters; optional CIFS/NFS gateway software

Software; disperses data slices across multiple locations; iSCSI interface

Data Direct Networks Web Object Scaler
Appliance-based object store; location-aware policy engine; up to 60 TB per node

EMC Atmos
Integrated hardware/ software; distributed objects; policy engine; supports multitenancy; minimum config is 120 TB

HDS Hitachi Content Platform
CAS/RAIN appliance; internal or external storage; replicates between clusters; supports multitenancy

IBM Business Storage Cloud
Cluster file system with integrated product and services; can use IBM XIV grid back end

ParaScale Cloud Storage Software
Software; distributed object copies; replicates among clusters

Symantec FileStore
Cluster file system software; uses shared storage; replicates file systems; supports multiple tiers

The CAS/RAIN vendors aren't the only ones using cloud labels to fog up product categories. Vendors like IBM and Symantec have repackaged their clustered file systems into private clouds. Symantec FileStore software wraps Storage Foundation, and its integrated VxFS clustered file system, in a package that's easier to install and manage. IBM's Smart Business Storage Cloud leverages its GPFS clustered file system along with XIV clustered block storage (and of course, IBM services).

While cluster file systems can deliver impressive performance, their reliance on expensive back-end storage makes them relatively pricey compared with RAIN architectures. Cluster file systems are more appropriate to applications, like render farms, that require high performance for individual clients.

Pick A Package

Organizations that want to get private cloud storage off the ground quickly, or prefer the comfort of one throat to choke, should consider integrated systems like Hitachi's Content Platform, EMC's Atmos, or Data Direct Networks' Web Object Store. These products come complete with storage hardware, software, processors--and in the case of Atmos, even the rack.

Those looking for cloud economics may prefer software like Bycast's StorageGrid, ParaScale's Storage Cloud, or Caringo's CAStor. Because these vendors charge for their software on a per- gigabyte basis, users can easily match capacity to cost. Meanwhile, Cleversafe sells pre-configured access, storage, and management nodes, and the adventurous can use the open source community version from

Private cloud storage systems can bring cloud economics to the data center, allowing corporate IT to retain control over data, security, and reliability. These new architectures promise to not only reduce the up-front cost of storing many terabytes of unstructured data but also reduce the amount of manpower required to manage it.

Howard Marks is chief scientist at Networks Are Our Lives, a consulting firm.