SAN File System is based on a client-server paradigm. A SAN File System client is a computer system that accesses and creates data that is stored in the SAN File System global namespace. A client can act as servers to a broader clientele, providing Network File System (NFS) or Common Internet File System (CIFS) access to the global namespace or hosting applications (for example, database servers or Web-hosting services that use multiple servers).
The SAN File System Protocol Specification includes a description of the protocols that are used between a metadata server and clients running on application servers. It is available at www.ibm.com/storage/software/virtualization/sfs.
Clients access metadata (such as a file's location on a storage device) only through the metadata server, and then access data directly from storage devices attached to the SAN. This method of data access eliminates server bottlenecks and provides read and write performance that is comparable to that of file systems built on bus-attached, high-performance storage.
SAN File System supports clients that run several UNIX® and Windows® operating systems. You must install client software on each client machine. On UNIX-based clients, the software is a virtual file system (VFS). On Windows clients, it is an installable file system (IFS). The VFS and IFS software provide clients with local access to the global namespace on the SAN. A VFS is a subsystem of a UNIX-based client's virtual file system layer, and an IFS is a subsystem of a Windows client's file system.
The VFS or IFS software directs all metadata operations to a metadata server and all data operations to storage devices attached to the SAN. The VFS or IFS software makes the metadata that is visible to a client's operating system, as well as any applications that the client runs, look identical to metadata read from a native, locally-attached file system —that is, it emulates the local file system semantics. In this way, client applications do not need to change their access methods to use SAN File System.
When the global namespace is mounted on a UNIX-based client, it looks like a local file system. When the global namespace is mounted on a Windows client, it appears as another drive letter and looks like an NTFS file system. Therefore, files can be shared between UNIX-based and Windows clients (permissions and suitable applications permitting).
Host-based clustering
This topic describes the cluster applications that you run on SAN File System clients.
Parent topic: Concepts
Related tasks
Starting an AIX client
Starting a Windows client