NAS Technology Is Ready For Prime Time.

Network Attached Storage (NAS) is emerging as a powerful, proven technology for meeting an organization's unquenchable demand for storing data, regardless of its source on the network. Three factors are accelerating end user demand for NAS and for a new generation of storage appliance offerings:

* Cost benefit to IT. NAS is an effective strategy for extending an organization's existing in vestment in server technology. NAS architecture allows IT organizations to add storage on the network without requiring any upgrade and/or replacement of the servers themselves.

* Administrative convenience. As a network-based solution, NAS-based storage offers administrative features that simplify or eliminate manual disk expansion and archiving functions, user and application partitioning, data protection, and other time-consuming storage maintenance activities.

* Network-based Unix and Microsoft NT integration. Leading NAS appliances can support storage of both Unix and NT files in the same device. The most sophisticated systems provide simultaneous CIFS/SMB (for NT) and NFS (for Unix) file sharing protocol support, as well as integration of Unix and Microsoft file system semantics to address file system-level compatibility. Network-based applications data can be shared among either Unix or NT clients; storage facilities can be dynamically reallocated; and, after installation, the NAS device can support data from any network-based application or client workstation. This dynamic support of Unix and NT file storage with minimal-to-zero administrative management provides IT with the highest degree of storage flexibility and the lowest TCO.

Delivering Unix/NT NAS Capability

For many organizations, storage requirements are almost doubling annually, fueled in part by electronic mailboxes (whose capacity requirements can double every three months) and data with increasing levels of video and graphic content. In response to explosive demands for storage, computer manufacturers will, over the next year, introduce a variety of NAS appliances aimed at every size and segment of the IT market. Many will include file systems with the ability to simultaneously support Unix and Microsoft Windows 95/98/NT. Administrators will be able simply to attach the appliance onto the network, redirect applications to NAS-maintained storage resources, and assign the appropriate user access. The NAS appliance will seamlessly manage the file security, integrity, and semantics of Unix and NT file systems.

The management of Unix/NT-capable NAS appliances is so simple that its technical sophistication may not be immediately apparent. Unix/NT-capable storage appliances must incorporate all the network connectivity of their application server counterparts and must deliver performance fast enough to satisfy network-connected clients. They have to incorporate design elegance for scalability, modularity, and integration with other network-based applications, such as backup, hierarchical storage management, and virus protection. They must insure reliability and often support fault-tolerance capability. And they must provide storage without imposing additional user complexity--in order to truly serve as just another stop on the network neighborhood.

To minimize system administration, one of the most important technical capabilities of a NAS device is the way it handles Unix/NT data sharing. Merely supporting the CIFS/SMB and NFS file sharing protocols limits the level of transparency for supporting NT and Unix data and, accordingly, the level of data sharing that can be achieved. Major file system semantic distinctions that exist between Unix and NT--in the way Unix and Windows/NT handle semantics for filenames, file attributes, shared file-locking techniques and their respective file security subsystems--are not resolved by CIFS/SMB and NFS file-sharing protocols. For truly transparent, seamless Unix/NT data sharing, the NAS appliance must include file-system-level capabilities that manage these semantic differences.

Windows Vs. Unix Filenames

Considerable differences exist between Windows filename semantics and Unix-style filename semantics, and NAS devices should provide the appropriate interface to the client accessing the system (Windows or NT) and should in all cases avoid compromising data security and integrity. Within the Windows environment, NAS devices must transparently support 8.3 short name aliasing features to manage the differences between filenames created with earlier releases of Windows and those created with current releases of Windows and Windows NT, which support up to 255 characters.

Implementing filename interface support at the file system level gives the NAS device the ability to prevent different client environments from creating files with duplicate names, thus avoiding a blatant security hole in the file system. Another filename issue is case semantics. In Unix systems, all filenames are case-sensitive. In Windows systems, filename case is preserved when the file is created, ignored for all other operations, and disallowed if it will create two files whose names differ solely incase. File-system-aware NAS devices have the intelligence to allow both sets of semantics to coexist in the same file system.

File Attributes

Similarly, NAS devices must be able to maintain the file attributes associated with the data they are storing and have the intelligence to manage the differences between Unix, NTFS, and Windows FAT file attributes. The Windows FAT file system, for example, was designed as a single-user file system for desktop workstations and does not incorporate concepts of users and permissions necessary for networking and/or shared data access associated with NTFS and Unix. To support the file system attributes of standalone Windows-compatible FAT systems, NAS systems must preserve Windows FAT file attributes for read-only, hidden-file, system-critical, and archive status.

Tim Williams is the president and CEO and Sue Smith is the corporate director of marketing at CrosStor Software, Inc. (South Plainfield, NJ).