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The new world of NAS virtualization: the next generation could fulfill NAS' promise. (Storage Networking).

Storage virtualization has been a key enabling technology for storage area networks (SANs). Virtualizing storage allows administrators to treat all available storage devices as a general pool of storage, which is presented to the application server as one big disk that can be expanded or modified dynamically without impacting storage availability to applications.

Virtualization is now playing a key role in a new generation of network attached storage (NAS) technology. This new NAS architecture breaks the limitations of traditional NAS architectures and allows administrators to implement global file systems across servers, allows creation of application-specific storage pools that precisely provision storage assets to match business requirements, and enables management of all of these implementations from a single management console easily and efficiently.

One of the limiting factors of NAS has been the inability of a NAS file system to scale beyond an individual server, introducing additional costs and complexity when storage capacity needs to be expanded or re-allocated. The new-generation NAS architecture is based on a distributed file system that incorporates many virtual features into the base system architecture to provide a complete solution to the scaling, performance, and management problems that have plagued the NAS industry.

The use of a distributed file system enables clustering of NAS servers into a single storage resource. This new architecture then implements and expands the storage virtualization paradigm by employing a series of virtual NAS functions. In the SAN arena, multiple virtualization schemes are available--software-based, hardware-based, appliance-based--each with specific strengths and weaknesses. The new NAS virtualization architecture rolls the best of all virtualization approaches into one NAS server by offering not just basic virtualization, but a more robust virtualization implementation that encompasses the entire realm of storage management. This new architecture includes virtual file system, virtual server, virtual interface, and storage pool components all designed to ease the burden of multi-server NAS management.

These innovations provide unprecedented NAS functionality, including:

* Transparent multi-server scaling of capacity and performance.

* Multi-server scaling of capacity and performance of a single file system.

* Global file system across multiple servers.

* Application-specific storage pools.

* Non-disruptive, online data movement.

* Single management console and management view across servers.

* Segregation of clients for secure resource sharing.

* Segregation of clients for logical management.

* Transparent client access port failover.

* Non-disruptive client access load distribution.

Virtual File System

The virtual file system (VFS) can be thought of as the universal storage container of the NAS storage system. A VFS can consist of a directory tree and associated files that can be viewed and manipulated as a singular storage container. A VFS may be assigned to a user, group of users or applications. VFSs have quotas and access permissions. Clients access files as they normally would using a standard NAS server using with? shares or mount points. The client files are stored in VFSs on the NAS server. The NAS server distributed file system takes responsibility for virtualizing or mapping the clients' actual shares or mount points to a particular VFS within the storage system. The distributed file system provides a de-coupling of the actual user's share or name space from the physical location of where the data or VFS resides. The users are unaware of the actual physical location of their data. It may be on a local NAS server or a NAS server in a different city. The virtual file system plays a big part in elimi nating location dependency and downtime required for reconfiguration and scaling because the file access has been de-coupled from the physical storage location.

Virtual Server

The architecture logically groups select storage resources into a single virtual server (VS) that can be assigned and relegated to a particular user community. Typically a virtual server would be configured with client access ports, VFSs, and an administrator. Virtual servers can span multiple physical servers that may be geographically dispersed. The virtual server handles the presentation of storage resources as a combined whole to the clients. Virtual servers provide segmentation and logical isolation of users on a shared set of resources, securely and transparently. It works by associating each virtual server with a set of network ports and a set of virtual file systems. Only requests from ports configured on a virtual server may access VFSs stored on the virtual server. Users only see VFSs associated with their respective virtual server. A virtual server may have one or more administrators, allowing multiple levels of storage management.

Virtual Interface

The virtual interface (VI) provides client access to a virtual server. A virtual interface is mapped to one physical interface on the NAS server. The virtual interface is then assigned to a specific user or user community. A virtual server may have one or more virtual interfaces assigned. Since a virtual server may span multiple NAS servers in a cluster, a single virtual server may have many virtual interfaces assigned on multiple NAS servers. In the event of a failure of a particular physical port, all virtual interfaces may be automatically and transparently failed over to partner virtual interfaces. For load balancing and load distribution, a single virtual interface may be migrated to another physical interface on the same or a different NAS server without user disruption. It is a straightforward but very important part of the NAS server virtual offering because it helps preserve performance, non-disruptive client access and support high-availability configurations.

Storage Pools

A storage pool is the aggregation of physical storage media into a logical storage pool. In this virtualized NAS architecture, each storage pool is comprised of one or more RAID sets, and can vary in size from less than ITB to 22TB. Because storage pools are comprised of physical storage, they may take on the characteristics of the underlying physical media. Storage pools are contained completely within an individual NAS server. RAID sets may be added to a storage pool online and without disruption. VFSs may take advantage of new capacity added to a storage pool instantaneously.

The configuration flexibility enabled with storage pools allows storage administrators to actually create application specific storage pools. By supporting different RAID configurations, different drive types, and different drive configurations, storage administrators are able to configure storage based on the business needs of different applications. For example, an application requiring high performance and high throughput--such as ecommerce--would assign its VFSs to storage pools comprised of low latency drives, and have a reasonably small number of drives in the RAID set for best performance. The storage pool may reside behind a NAS server that is used solely for this application providing 100% of the server processing power to the single application. Conversely, a large library access application would assign its VFSs to a storage pool that is configured using slower drives with higher capacity, and use RAID sets with a very large number of drives that minimize storage costs. Configuration may now be dr iven by business need, not by technology.

Virtual NAS in Action

One example of the power of the new NAS virtualization architecture would be an enterprise undertaking a storage consolidation project. In this example, an enterprise with four separate physical locations (corporate, business unit 1 (BU1), business unit 2 (BU2), and business unit 3 (BU3)) each with their own data centers wishes to consolidate operations to the corporate headquarters location, while minimizing operational im-pact. The individual business units are to retain individual control of their storage resources while corporate needs to have global control, viewing, and management capabilities.

Using the virtual capabilities of the new architecture, centrally located storage is deployed at the main data center. The storage is then assigned into virtual servers, one for each business unit, and resources such as virtual server administrator and virtual interfaces are added. Once the physical pooling and connections are in place, the NAS server is used to recreate and implement the storage environment that existed when the business units were physically distributed. The data can be moved non-disruptively across the distributed scalable cluster to the new location, easing the burden on the storage administrator, allowing the move to occur even while the data is in use. Once the data is moved, the end-users will access their data and files as they normally did prior to the consolidation. The integrated distributed file system handles the mapping of the actual share or mount point to the appropriate VFS, and the users' shares or mounts never had to be modified-the virtual aspect of the architecture handl es the mapping. The virtual server groups and manages access to VFSs spanning multiple storage pools that can reside at different geographic locations, allowing the corporate administrator to have true global control and management.

Users at all four locations view and store files on their particular directories unaware of any physical changes. BU1, BU2, and BU3 all have control of their respective storage and corporate can manage and control the entire cluster from a single console as a single entity. When extra capacity is needed, it can be added and made available immediately without disruption to the end-users. The same goes for the addition of a new server to the existing file system or for moving data from one server to another. In addition, if a physical interface ever fails, the associated virtual interface may be migrated to a different physical interface on the same or different server. This occurs behind the scenes without any end-user disruption. Last but not least, the corporate administrator can associate enterprise applications with virtual servers based on the performance and availability requirements creating application specific storage pools designed to meet the needs of the business.

One such next-generation NAS solution that exemplifies the potential of NAS virtualization is Spinnaker Networks' recently introduced SpinServer 3300, which brings features and performance never before available in a NAS server.

Next-generation NAS solutions deliver the virtual NAS capabilities considered essential in a comprehensive enterprise storage network without introducing additional management issues or complexity. Management costs are significantly reduced through a single point of management and non-disruptive data movement and scaling features. Downtime costs associated with normal storage administration functions can be a thing of the past. The ability to create application-specific storage pools ensures that an organization will maximize the ROI of its storage expenditures. The future of enterprise NAS is virtually assured.

Mark Buczynski is senior marketing manager at Spinnaker Networks (Pittsburgh, Pa.)
COPYRIGHT 2002 West World Productions, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
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Article Details
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Title Annotation:network attached storage
Author:Buczynski, Mark
Publication:Computer Technology Review
Geographic Code:1USA
Date:Nov 1, 2002
Previous Article:SATA vs. PATA: the reality of Serial and Parallel ATA. (Serial ATA).
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