Abstract
This Tip explains what a SAN is and what it does.
Contents
What is a SAN? One definition of a Storage Area Network (SAN) is a high-speed network, comparable to a LAN, that allows the establishment of direct connections between storage devices and processors (servers) centralized to the extent supported by the distance of Fibre Channel. The SAN can be viewed as an extension to the storage bus concept that enables storage devices and servers to be interconnected using similar elements as in Local Area Networks (LANs) and Wide Area Networks (WANs): routers, hubs, switches, directors and gateways. A SAN can be shared between servers and/or dedicated to one server. It can be local or can be extended over geographical distances.
SANs create new methods of attaching storage to servers. These new methods can enable great improvements in both availability and performance. Today’s SANs are used to connect shared storage arrays and tape libraries to multiple servers, and are used by clustered servers for failover. They can interconnect mainframe disk or tape to mainframe servers where the SAN switch devices allow the intermixing of open systems (Windows, AIX, etc) and mainframe traffic.
A SAN can be used to bypass traditional network bottlenecks. It facilitates direct, high speed data transfers between servers and storage devices, potentially in any of the following three ways:
- Server to storage: This is the traditional model of interaction with storage devices. The advantage is that the same storage device may be accessed serially or concurrently by multiple servers.
- Server to server: A SAN may be used for high-speed, high-volume communications between servers.
- Storage to storage: This outboard data movement capability enables data to be moved without server intervention, thereby freeing up server processor cycles for other activities like application processing. Examples include a disk device backing up its data to a tape device without server intervention, or remote device mirroring across the SAN.
Why would I want one? SANs allow applications that move data to perform better, for example, by having the data sent directly from source to target device without any server intervention. SANs also enable new network architectures where multiple hosts access multiple storage devices connected to the same network. 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 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 attack.
- Simplified centralized management: Single image of storage media simplifies management.
Today, Fibre Channel (FC) is the architecture on which most SAN implementations are built. Fibre Channel is a technology standard that allows data to be transferred from one network node to another at very high speeds. Current implementations transfer data at 1 Gb/sec. or 2 Gb/sec., and 10 Gb/sec. data rates have already been tested and many companies have in their development products that will support this requirement. This FC standard is accredited by many standards bodies, technical associations and vendor and industry wide consortiums. There are many products on the market that take advantage of FC’s high-speed, high-availability characteristics.
Special Notices
This material has not been submitted to any formal IBM test and is published AS IS. It has not been the subject of rigorous review. IBM assumes no responsibility for its accuracy or completeness. The use of this information or the implementation of any of these techniques is a client responsibility and depends upon the client's ability to evaluate and integrate them into the client's operational environment.