NAS

While clustered storage is often associated with high performance computing, the reality is that organization are adopting adopting clustered storage at a rapid rate.

 These organizations are attracted by the way clustered storage uses technologies

• Ethernet,
• Fibre Channel
• InfiniBand protocols,

by its reliance on open access methods such as NFS and Windows CIFS, and by its use of industry-standard servers and third-party storage.

The clustered storage solutions that are growing in popularity are network attached storage (NAS) file servers. Deployments of this technology are being driven by the need of organizations to scale beyond the limits of a single storage box to handle structured and unstructured data.

Clustered NAS systems offer scaling advantages on many levels:

• scaling in performance of large sequential bandwidth (throughput) or small random IOPS (transactional) and meta data lookup;
• scaling in storage capacity;
• scaling availability on a local or distributed basis to isolate against device or site failure;
• scaling of flexibility, including concurrent access of the same or different data along with parallel access of data for different application needs;
• scaling in terms of offering modular (pay-as-you-grow) storage growth; and
• scaling in ease of manageability of tasks such as provisioning of storage, load balancing and data protection.

Approaches to NAS and file serving clustering

The technologies that most companies are clustering are storage, file systems and file servers.

Clustering adds standby or failover capabilities to storage systems that in turn support scaling with a large number of controllers, storage nodes or processors along with clustered file systems.

One reason for the confusion in discussions of clustered storage is that there are block-based (iSCSI and Fibre Channel) and file-based (NAS NFS and CIFS) storage, virtual tape libraries and other types of clustered storage solutions.

Clustered file systems enable administrators to access a common pool of storage across application servers. Clustered file systems also permit shared access (read and write) of data files, which is useful for maintaining data consistency and integrity whether using direct-attached or networked storage.

What differentiates a clustered fileserver from a traditional NAS file server or clustered storage system is the way hardware and software is combined.

A clustered file system can be installed on application servers or on dedicated appliances or servers, transforming them into storage servers (essentially, becoming a clustered fileserver).

Some vendors who have dual or redundant storage controllers, storage engines, NAS heads or gateways using active/active (both controllers working) or active/passive (one controller in standby) modes claim to offer clustered storage systems.

A pair of storage processors or controllers as a cluster, you’d have to consider every storage system with at least two nodes a cluster. . .which would encompass pretty much all of the mid-range SAN, DAS and NAS storage systems in the marketplace.

NAS, by its nature, is a file serving solution that sits on top of hardware and in some cases has the ability to transform the hardware into a clustered fileserver