
The storage is then shared over some network topology using protocols like NFS.

This model uses one or more large workstations or file servers to locally attach the shared disk storage. The most prevalent storage model is server-attached. In a typical data processing center today, there may be many different methods of sharing storage among multiple workstations. * The Server-Attached Shared Storage Model. Then, we will address important SAN FS features such as configuration, data placement strategies, cross platform data sharing, fault tolerance, and performance. We will discuss the difference between a typical server-attached shared storage model using NFS and a distributed network-attached storage model using Mountaingate's CentraVision File System (CVFS). This article will discuss how a SAN File System (SAN FS) operates. In the last three or four years however, a number of mostly third-party vendors have begun developing and offering distributed file system solutions that exploit the SAN distributed environment.
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The early SAN devices were used only in a server-attached shared storage environment because of this problem and due to no readily available software solution. If the file system accesses the storage without coordination with other workstations in the network and two or more inadvertently share access to the network-attached storage devices, data corruption occurs. Existing local file systems such as Microsoft's NTFS 1, SGI's XFS, and Apple's HFS assume that any visible storage, whether in a network or locally connected, is owned by the local workstation. At the core of every operating system are file systems that abstract disk storage and allow multiple programs to reliably share this resource.

What has been missing from the formula is the ability for software to leverage the distributed nature of the storage network. In and by themselves, they offer a high-speed access method to storage. Many vendors have committed resources to developing hardware products that comprise a SAN by producing a variety of Fibre Channel compatible hardware components. This concept has started a new surge of distributed storage product development and has been coined the "SAN solution." The new connectivity obviates the need for a server and promotes a more distributed approach to managing data. The distinct difference between using the conventional server-attached storage shared file system and a SAN is that any workstation connected to the network fabric can directly access the network-attached storage devices. This capability provides a storage network that is highly scalable, has high performance, and allows complete sharing of any connected device. The Fibre Channel protocol uses addressable nodes in such a way that storage devices can be configured in a network fabric rather than point-to-point. Fibre Channel is a high-speed (100MB/sec) channel that is capable of connection distances measured in kilometers.

The network, which includes HBAs, hubs, switches, and network-attached storage, is called a Storage Area Network (SAN). Using compatible Fibre Channel Host Based Adapters (HBAs), any work-station can address the storage and access data to and from it, just as it would do to a directly connected SCSI storage device. With the advent of open standard technologies such as Fibre Channel and its ability to imbed SCSI commands, it is possible to connect mass storage directly into a network at relatively low cost. These products are still a very large part of today's shared storage solutions. They started as simple systems using file server protocols such as the Network File System (NFS). Various shared file systems have been in use for more than fifteen years. Finally, we will show that distributed file systems can provide superior performance over traditional server-attached storage shared file systems.
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The remainder of the article will focus on issues of DFS configuration, data placement strategies, cross platform data sharing, fault tolerance, and performance. Throughout the discussion, the traditional server-attached storage model is compared against the distributed network-attached storage model. Many desirable features make a SAN DFS attractive to a production environment that processes huge volumes of bulk data and requires high bandwith. This article discusses some fundamental aspects of Distributed File Systems (DFS) for Storage Area Networks (SANs). APA style: Distributed File Systems For Storage Area networks.Distributed File Systems For Storage Area networks." Retrieved from
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