Storage area networks
The Storage Networking Industry Association (SNIA) defines the storage area network (SAN)
as a network whose primary purpose is the transfer of data between computer systems and
storage elements. A SAN consists of a communication infrastructure, which provides physical
connections. It also includes a management layer, which organizes the connections, storage
elements, and computer systems so that data transfer is secure and robust. The term SAN is
typically (but not necessarily) identified with block I/O services rather than file access
In simple terms, a SAN is a specialized, high-speed network that attaches servers and
storage devices. The SAN is sometimes referred to as the network behind the servers. A SAN
allows an any-to-any connection across the network, by using interconnect elements, such as
switches and directors. The SAN eliminates the traditional dedicated connection between a
server and storage, and the concept that the server effectively owns and manages the storage.
The SAN also eliminates any restriction to the amount of data that a server can access.
Traditionally, a server is limited by the number of storage devices that attach to the individual
server. Instead, a SAN introduces the flexibility of networking to enable one server or many
heterogeneous servers to share a common storage utility. A network might include many
storage devices, including disk, tape, and optical storage. Additionally, the storage utility might
be located far from the servers that it uses.
The SAN can be viewed as an extension to the storage bus concept. This concept enables
storage devices and servers to interconnect by using similar elements, such as LANs and
wide area networks (WANs).
SANs create new methods of attaching storage to servers. These new methods can enable
great improvements in both availability and performance. The SANs of today are used to
connect shared storage arrays and tape libraries to multiple servers, and they are used by
clustered servers for fail-over.
A SAN can be used to bypass traditional network bottlenecks. A SAN facilitates direct,
high-speed data transfers between servers and storage devices, potentially in any of the
following three ways:
Server to storage: This method is the traditional model of interaction with storage devices.
The advantage is that the same storage device might be accessed serially or concurrently
by multiple servers.
Server to server: A SAN might be used for high-speed, high-volume communications
Storage to storage: This outboard data movement capability enables data to be moved
without server intervention, therefore freeing up server processor cycles for other
activities, such as application processing. Examples include a disk device that backs up its
data to a tape device without server intervention, or a remote device mirroring across the
SANs allow applications that move data to perform better, for example, by sending data
directly from the source device to the target device with minimal server intervention. SANs
also enable new network architectures where multiple hosts access multiple storage devices
that connect to the same network.
The use of 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 offloaded from servers and moved
onto a separate network.
Centralized and consolidated storage: Simpler management, scalability, flexibility, and
availability are possible.
Data transfer and vaulting to remote sites: A remote copy of data is enabled for disaster
protection and against malicious attacks.
Simplified centralized management: A single image of storage media simplifies
Storage area network storage
The SAN liberates the storage device so that the storage device is not on a particular server
bus and attaches it directly to the network. Storage is externalized. It can be functionally
distributed across the organization. The SAN also enables the centralization of storage
devices and the clustering of servers, which potentially can help you achieve easier and less
expensive centralized administration that lowers the total cost of ownership (TCO).
The storage infrastructure is the foundation on which information relies. Therefore, the
storage infrastructure must support the business objectives and business model of a
company. In this environment, simply deploying more and faster storage devices is not
enough. A SAN infrastructure provides enhanced network availability, data accessibility, and
Components of a Storage Area Network (SAN)
Multiple servers, from different vendors, on different operating systems can all be connected to a Storage Area Network (SAN). Unlike DAS (Direct Attached Storage), all servers connected to the Storage Area Network (SAN) can share all of the storage available, which reduces the overall cost per megabyte for your business.
Storage Area Network Fabric
The Storage Area Network (SAN) Fabric is effectively the SAN network that connects the servers to the storage. The Storage Area Network (SAN) Fabric is made up of 2Gb fibre channel switches (supplied by multiple vendors including CISCO, Brocade and IBM) which manage the connectivity from the servers HBA (Host Bus Adaptor) to the Storage Area Network (SAN) storage.
Host Bus Adaptors (HBA’s)
PCI adaptor connects a server to the SAN fabric. Each HBA installed is referred to as a host. Two HBA’s can be installed into each server for additional resilience.
High speed fibre optic cabling used to interconnect between servers, storage and tape backup devices.
Linking a tape library into the Storage Area Network (SAN) Fabric provides a fast and reliable solution to backup critical data. Data stored on the Storage Area Network (SAN) is transferred directly to the tape library, using “serverless” technology. This reduces the load on each server and ensures data is backed up within the time window available.
The software enables individual components to be configured and optimized for performance. It monitors network for bottlenecks enabling IT Managers to preempt problems and adjust accordingly.
Centralized Data Storage and Backup Management
Storage Area Networks (SAN’s) can provide an effective solution to the data storage demands of businesses today. With an estimated annual data growth of many companies, in excess of 100%, and data legislation on the increase, the storage and management of data is a critical issue. The amount of data stored in servers is constantly increasing and this is exposing the limitations of traditional storage devices where up to 50% of existing capacities can be unused due to their inherent nature.
The growth in data storage is also exposing the limitations of traditional back up devices, leading to increased downtime and insufficient protection in the event of a disaster. Businesses must look for new solutions to meet the demands of today’s data storage and back up requirements. One such solution for data storage and effective backup management is to implement a Storage Area Network.
If your business is hindered by any of the following, then a Storage Area Network (SAN) may be the right option for your business.
- Complex multiple server environment
- Insufficient data storage capabilities
- Low scalability
- High administration costs associated with protecting data
- Insufficient network data protection
- Poor data access, especially for tape back ups and restoration
- Inability to meet data storage legislation requirements / regulatory compliance