As NAS systems become more prevalent in enterprise environments, the needs for greater capability and capacity become more apparent. The definition of a "high-end" NAS system and its characteristics are not readily apparent and certainly are not agreed upon by vendors or customers. Identifying some of these characteristics and understanding their value should help in discussing the products available from vendors to meet customer needs. There are different implementations to address customer needs in a high-end NAS system, and the implications of how the implementation is carried out needs to be considered by each customer.
Characteristics of a high-end NAS system
There are certain characteristics needed in NAS systems for demanding enterprise environments that distinguish the products from those that are used in mid-tier, small to midsize business or departmental/workgroup environments. The individual importance of the characteristics may vary depending on the specific customer business requirements, but will have a degree of commonality across the high-end enterprise market.
The need to scale in more than one dimension is driven by the business requirements that have led to the deployment of NAS in the larger enterprise environments. The predominant case for deployment is consolidation of multiple file servers to a common, centrally managed resource; using NAS to provide file serving for multiple servers for use in applications, data sharing and as user file storage is basic to deployment. In those enterprise environments, the demand for capacity continues while the spending for IT administration is being held at nominal levels. Consequently, consolidation and minimization of administration makes NAS an attractive solution.
Increases in capacity and commensurate increases in performance are needed to be able to meet demands without introducing additional administrative efforts. This means larger and faster NAS systems that are managed as a single resource, as opposed to individually managed devices. There are many approaches to address the means to implement scaling.
From a capacity standpoint, there is more to consider with NAS than just the number of bytes that can be stored. The consideration has to include the number of files that can be supported in a file system, the number of file systems that can be supported, the size of individual files (and the implication of the overall size of a file system) and the number that can be open simultaneously. The performance implications include the number of simultaneous data paths that can be active that scale with the capacity increase, the aggregate bandwidth supported and the number of transactions supported within the response time required. Performance information for NAS products with NFS accesses is available on this Web site. There are special applications for NAS in areas like digital imaging, video streaming and the transferring of large files that may require some specific characteristics of a product.
The need to reduce administrative efforts leads to a discussion about presenting a "single image" for the high-end NAS system. With a single image, the administration is supportive of a single solution, even with the scaling of multiple NAS. This has several benefits beyond the ability to create a single namespace or multiple independent namespaces from a single image management perspective.
In terms of reporting, the high-end NAS system presents information as a single entity but can initiate alerts and actions at a more granular level. In the enterprise environments that deploy these systems, the ability to do chargeback for resource consumption is usually necessary, which is a characteristic not normally seen in NAS systems used in other environments. Interaction with storage management software, such as storage resource management (SRM), is also becoming a necessity and the adherence to SNIA's Storage Management Information Specification (SMI-S) will become a requirement.
Security mechanisms are very important in the enterprise environment and may go beyond the typical permissions for access that are usually implemented with NAS. Requirements for IP security and even encryption of data may be demanded by some customers, and will be a differentiating factor for some products.
The availability of access to data on a NAS system is a critical element in enterprise environments; it's monitored and may have financial implications for meeting requirements. Availability is typically accomplished by having more than one control function (node, controller or "head") having access to data such that if one fails, the data can still be accessed through another path. The overall impact of a controller failure, in regards to performance, is another business requirement element that will lead to specific product choices by customers.
Some of the features offered on NAS systems become requirements in enterprise environments, and the implementations of those features may be the difference for a customer in choosing one product over another. The completeness of a set of features also may be crucial to making a selection. The features needed in enterprise environments include:
- Asynchronous and synchronous remote replication for file systems over a network managed by the NAS system.
- Data migration capability to do consolidation and NAS system replacement.
- Load balancing in multiple node environments.
- Point-in-time copy for replication and data protection.
- Regulatory compliance on a selective basis.
- Integration with applications such as databases (including e-mail).
- Backup and restore enablement such as with NDMP.
- Tiered storage with automatic movement between difference classes of disks in the NAS system.
In part two of High-end NAS considerations, we'll look at the different implementations currently available to meet enterprise requirements. These implementations include clustered NAS solutions, very large NAS boxes and a system of federated nodes to share information and scale with node addition. Also in part two, the customer considerations will be examined. These will be focused on making informed decisions.
This was first published in August 2005