Storage Area Network (SAN)

Storage Area Network is used as a high-speed sub-network of shared storage devices. A storage device is a machine, which uses a disk or disks for storing data. Its architecture operates in such way that makes all storage devices accessible to all servers on a LAN and WAN. If more storage devices are attached to it then they too will be accessible from any server in the larger network. In SAN’s case, the server simply works as a pathway between the end user and the stored data. As stored data doesn’t reside directly on any of a network's servers and server power is used for business applications and network capacity is released to the end user.

Storage Area Network works behind the servers to provide a common link between servers and storage. It provides administrators to independently scale the storage or server processing power as per requirements. It provides multiple servers to access the same data so that duplication of information can be decreased and allows data backup to take place directly over storage channels eliminating the bottleneck of the relatively slow LAN. Data is available more consistently as the failure of a single server will not cut off any storage from remaining servers.

Why to implement SAN?
There are number of reasons for implementing a SAN.

A) SANs are cost effective :
1) It reduces cost of storage management including backup & recovery.
2) It increases user productivity.

B) SANs reduce business risk
1) It provides faster disaster recovery, reduced revenue loss from down-time.
2) It reduces lost opportunity costs.
3) Legacy investments are protected
4) It can be implemented without abandoning existing storage infrastructures such as devices using SCSI connections

C) SANs provide scalability
1) It is suitable for work-groups, which expand to support enterprise data centers.
2) It adds servers and storage independently.

D) SANs allow flexibility
1) It reconfigures Storage and Servers on the fly.
2) It provides load sharing and redistribution.

E) SANs enhance overall system performance
1) It improves performance by using existing server computes cycles.
2) It provides Real-time backup without impacting LAN/WAN.
3) It provides multiple servers to storage paths.

F) SANs are an integral part of any High-Availability plan
1) It reduces down time requirements.
2) Its Storage is independent of the application and accessible through alternate data paths such as found in clustered systems, even in "shared nothing" architectures.

SAN Components
SAN implementation built on Fiber Channel’s architecture with FICON as the standard protocol for S/390 systems and FCP as the standard protocol for non-S/390 systems. Based on this observation, the SAN components described as follows:

1) SAN Servers
SAN implementation built on Fiber Channel’s architecture with FICON as the standard protocol for S/390 systems and FCP as the standard protocol for non-S/390 systems. This infrastructure consist a mix of server platforms such as Windows NT, UNIX. With initiatives such as Server Consolidation and e-Business, the need for SAN will increase. Although the early SAN solutions only provide homogeneous environments, SAN will develop into a truly heterogeneous environment.

2) SAN Storage
The storage infrastructure is the base on which information depends and therefore must provide support a company’s business objectives and business model. In this situation, simply arranging more and faster storage devices is not enough; a new kind of infrastructure is required, which offers more improved network availability, data accessibility and system manageability than is provided by today’s infrastructure.

3) SAN Interconnects
The first element of any SAN implementation is the connection between storage and server components using technologies such as fiber channel. SANs interconnect the storage interfaces together into many network configurations and across long distances.

SAN Management
To accomplish the various benefits and features of SANs like availability, cost, scalability, performance, interoperability, the infrastructure of the SANs as well as the attached storage systems must be effectively managed. To simplify SAN management, SAN vendors require to adjust Simple Network Management Protocol (SNMP), Web Based Enterprise Management (WBEM) and Enterprise Storage Resources Management (ESRM) type standards to constantly monitor, alert and manage all components of the SAN.
There is also a need for organizing partitions of the SAN from a central console.

1) Asset Management
Asset management addresses the need to find out resources, identify the resources and tie them with the rest of the topology. The output is a complete recorded list of the assets that consists manufacturer, model information, software and license information.

2) Capacity Management
Capacity management related with sizes of the SAN. It also defines the need to know about free space/slots, unassigned volumes and free space in the assigned volumes, number of backups, number of tapes, percent utilization and percentage free/scratch.

3) Configuration Management
Configuration management related with need for current logical and physical configuration data, ports utilization data and device driver data to provide support to set SAN configurations based on business requirements of high availability and connectivity. It is also related with the need of integrating the configuration of storage resources with configuration of the server’s logical view of them.

4) Performance Management
Performance management related with the need to improve performance of SAN and do problem isolation at all levels like device hardware, software interfaces, application and file level. This approach needs common platform-independent access standards across all SAN solutions.

5) Availability Management
Availability management related with the need to prevent failure, correct problems as they happen and provide warning of the key events long before they become critical.

SAN Applications
SAN provides a number of applications that provide enhanced performance, manageability and scalability to IT infrastructures. These applications are as follows:

1) Shared Repository and Data Sharing
SANs allow storage to be externalized from the server and centralized and in so doing permit data to be shared among multiple host servers without impacting system performance. The term data sharing defines the access of common data for processing by multiple computer platforms or servers. Data sharing takes place between platforms that are similar or different; this is also known as homogeneous and heterogeneous data sharing.

2) Storage Sharing
Homogeneous or heterogeneous servers share a single storage subsystem with storage sharing, whose storage capacity has been physically partitioned so that each connected server can access only the units allocated to it. Multiple servers can share the same partition but this is possible only with homogeneous servers.

3) Data-Copy Sharing
Data-copy sharing provides different platforms to access the same data by sending a copy of data from one platform to the other. There is two data-copy sharing approaches between platforms: flat file transfer and piping.

4) Data Interchange
Data interchange primarily includes moving data from one storage system to another. SAN exchange data between different heterogeneous systems as one of the goals for SAN. This is primary goal because for data encoding and file structures different platforms store and access data using different methods.

5) Data Protection and Disaster Recovery
The application requires avoiding traditional recovery techniques such as recovery from tape. Instead of it, new techniques, which duplicate data must be architected so that upon the event of a failure, another system is ready to go. Techniques to duplicate the data portion consists remote copy and warm standby techniques.

Data protection is best achieved by creating second redundant copies of the data by storage mirroring, remote cluster storage, Peer-to-Peer Remote Copy (PPRC) and Extended Remote Copy (XRC), Concurrent Copy and other High Availability (HA) data protection solutions. These are used for disaster recovery situations.