18-01-2013, 03:49 PM
Storage Area Networks
Storage Area.ppt (Size: 109 KB / Downloads: 91)
Storage Area Networks - Defined
The Storage Networking Industry Association defines Storage Area Networks as follows:
A network whose primary purpose is the transfer of data between computer systems and storage elements and among storage elements. Abbreviated SAN. A SAN consists of a communication infrastructure, which provides physical connections, and a management layer, which organizes the connections, storage elements, and computer systems so that data transfer is secure and robust. The term SAN is usually (but not necessarily) identified with block I/O services rather than file access services.
A storage system consisting of storage elements, storage devices, computer systems, and/or appliances, plus all control software, communicating over a network.
SANs originated in the 1980s as a mainframe solution to storing large amounts of data that was scalable and flexible with highly availability.
Storage area networks (SANs) are high performance networks dedicated to delivering data between servers and storage.
Storage Area Networks - Architecture
A SAN consists of a communication infrastructure, which provides physical connections, and a management layer, which organizes the connections, storage elements, and computer systems so that data transfer is secure and robust.
Centralized and interconnected storage devices reside in the bottom tier of the traditional 3-tiered client/server architecture.
Fibre Channel is the most widely used SAN technology because of its speed, scalability and flexibility.
A SAN is typically based on one of two topologies:
Arbitrated Loop is a classic ring topology that manages traffic flow. It is a fairly inexpensive configuration for small and medium sized SANs.
Switched Fabric provides full duplex communication between all devices in the SAN. Fabric switches are considerably more expensive than an arbitrated loop hub, but can provide each device on the SAN an independent connection to every other device.
Storage Area Networks – Benefits
Using a SAN can potentially offer the following benefits:
Improvements to application availability: Storage is independent of applications and accessible through multiple data paths for better reliability, availability, and serviceability.
Higher application performance: Storage processing is off-loaded from servers and moved onto a separate network.
Centralized and consolidated storage: Simpler management, scalability, flexibility, and availability.
Data transfer and vaulting to remote sites: Remote copy of data enabled for disaster protection and against malicious attacks.
Simplified centralized management: Single image of storage media simplifies management.
Storage Area Networks – Management
SAN Storage Level
Consists of storage devices such as disks, disk arrays, tapes and tape libraries.
The ANSI SCSI-3 serial protocol is used by many SAN vendors in order to offer higher speeds, longer distances, and greater device population for SANs, with few changes in the upper level protocols. This protocol defines a new set of commands called SCSI Enclosure Services (SES) for basic device status from storage enclosures.
Storage Area Networks – Fibre Channel
Fibre Channel is the predominate SAN technology since it:
Provides a high-speed, non-blocking architecture
Scales from 133 Mbps to 1 Gbps and beyond
Allows different high-level protocols (IP, ATM, etc.) to operate over its infrastructure
Can connect nodes up to 10 kilometers (over 6 miles) apart.
Fibre Channel can attach devices through a number of methods like loops, hubs, and switches.
Hubs make loop simulate a series of point-to-point connections.
Switches permit multiple devices to be connected via multiple loops, thereby multiplying bandwidth. Multiple 100-MBps loop configurations can be managed through one central point.
Fabrics, composed of multiple switches, enable Fibre Channel networks to grow to very large sizes, that offer extremely high bandwidth. Fabrics can span very large geographic areas.
These features make fibre channel a fast, stable, and flexible technology for storage area networks.