automatically reallocate the space without disruption. If a LUN is removed from the SAN File System control, the data on that LUN is automatically moved. SAN File System helps reduce TCO by simplifying the management of files in a storage network. No application changes are required to realize these benefits. SAN File System offers a logical extension to current NAS and SAN environments. Our approach to NAS for customers with SANs is to add NAS capabilities to the SAN File System, therefore, allowing storage administrators to manage the NAS file data with the same tools they use for their application servers and SAN File System. Data does not have to be duplicated across multiple NAS devices. This approach of SAN/NAS convergence can lower TCO in these environments. In summary, the SAN File System is a common SAN-wide file system that permits centralization of management and improved storage utilization at the file level. SAN File System is delivered in a highly available configuration based on IBM eServer xSeries with clustering for the meta-data controllers, providing redundancy and fault tolerance. SAN File System is designed to provide policy-based storage automation capabilities for provisioning and data placement, non-disruptive data migration, and a single point of management for files on a storage network. The use of the SAN File System can greatly help simplify the management of files on SANs and result in a significant reduction in TCO. The IBM TotalStorage SAN File System is designed on industry standards, so it can: Allow data sharing and collaboration across servers over the SAN with high performance and full file locking support, using a single global namespace for the data. Provide more effective storage utilization by reducing the amount of duplicate data and by sharing free and temporary space across servers. Improve productivity and reduce the "pain" for IT storage and server management staff by centralizing and simplifying management through policy-based storage management automation, therefore, significantly lowering the cost of storage management. Facilitate application server and storage consolidation across the enterprise to scale the infrastructure for storage and data on demand. Simplify and lower the cost of data backups through built-in, file-based FlashCopy image function. Eliminate data migration during application server consolidation, and also reduce application downtime and failover costs. 5.6 IBM System Storage N Series All of the IBM N Series models are powered by a specialized OS ­ Data ONTAP which is designed to offer the best networked storage performance and data availability. The N Series reduces complexity by using an "appliance" philosophy; keep it simple by doing one thing but do it better than anyone else. Data ONTAP is specifically designed for storage and is simpler to use than general purpose OSs such as Windows or Unix. The flexibility in N Series hardware provides a "future proof" investment for enterprises ­ no matter which file sharing protocols (CIFS, NFS, FTP, or HTTP) and storage connections (FCP or iSCSI) are used, N Series hardware can be plugged into any of these environments. Write AnyWhere File Layout Data ONTAP incorporates the highly optimized WAFL (Write Anywhere File Layout) file system and storage virtualization layer that is designed to minimize disk head movement for efficient reads and writes. With every write to the file system, the N Series stripes the data to Chapter 5. Storage virtualization 103