Cluster name space (CNS)

Server and Cluster Administration Guide for Hitachi NAS Platform

Part Number

A Cluster Name Space (CNS) allows multiple separate file systems on a server to appear as subdirectories of a single logical file system (that is, as one unified file system). They can also make multiple storage elements on that server available to network clients through a single CIFS share or NFS export.

The root directory and subdirectories in the CNS tree are virtual directories. As in a file system, the root occupies the highest position in the CNS tree and subdirectories reside under the root. Access to these virtual directories is read-only. Only the server's physical file systems support read-write access. Physical file systems can be made accessible under any directory in the CNS tree by creating a file system link. File system links associate the virtual directory in the CNS tree with actual physical file systems.

Any or all of the subdirectories in the CNS can be exported or shared, making them (and the underlying physical file systems) accessible to network clients. Creation and configuration of a CNS can be performed through the NAS Manager or the CLI.

After shared or exported, a CNS becomes accessible through any EVS on its server or cluster. Therefore, it is not necessary to access a file system through the IP address of its host EVS and, in fact, file systems linked into the CNS can be relocated between EVSs on the server or cluster transparently and without requiring the client to update its network configuration. This accessibility can be useful in distributing load across cluster nodes.

The simplest CNS configuration is also the most common. After creating the root directory of the CNS, create a single CIFS share and NFS export on the CNS root; then, add a file system link for each physical file system under the root directory. Through this configuration, all of the server's storage resources are accessible to network clients through a single share or export, and each file system is accessible through its own subdirectory.

Windows and UNIX clients can take full advantage of the storage virtualization provided by CNS, because directories in the virtual name space can be shared and exported directly.

Tip: For the best results, FTP mount points and iSCSI logical units (LUs) should be added to file systems that are not part of a CNS, as CNS does not support FTP mount points or iSCSI LUs. Because FTP clients and iSCSI Initiators communicate directly with individual EVSs and their associated file systems, connectivity for any file system containing FTP mount points or iSCSI LUs must be reestablished through a new EVS upon relocation.
Note: CNS is a licensed feature. To create a Cluster Name Space, a CNS license must be installed. To purchase a CNS license, contact customer support.