Although SANs are becoming a more and more popular means to solve storage  

needs, a standardized methodology to evaluate the needs of companies wishing to implement a storage solution does not exist.  This SAN Analysis and Design  

Methodology creates a SAN analysis and design that could not only be used to create the most cost effective SAN solution that will work best for every unique scenario, but it could also determine if a SAN is indeed the solution to a company’s storage needs or if a Network Attached Storage (NAS) or Direct-Attached Storage (DAS) solution might be preferable. 

This matrix will enable an organization to determine the following five building blocks that should be assessed to determine “how the supported applications affect the entire data environment,” as well as the Interface, Interconnects, and Fabric.

         Application requirements

         Data storage requirements

         Backup and disaster tolerance

         Server connectivity requirements tolerance

         Performance and growth

To keep the length of this document reasonable and I will not elaborate on physical definitions of SAN Interfaces and Interconnects. This is a high level overview of technologies used in building SAN Infrastructures.   


Why SANs?  

E-business has caused explosive growth in data storage needs through data warehousing, e-commerce, and Enterprise Resource Planning (ERP).  These applications demand 100% data availability to customers and employees.   

Government regulations require “high levels of system and data backup” for  

healthcare, banking, and financing industries.

Data is now one of the most valuable assets a corporation can have.  In assuring its availability, integrity, and disaster recoverability, storage is now the most important IT resource for these mission-critical components.The loss of data availability and integrity can cause severe and sometimes fatal damage to a corporation.   

Today, data must be readily available to applications as well as departments with

corporations.  Storage networking is now a strategic component of the IT infrastructure.

Storage Area Networks (SANs) have gained recognition as the potential solution to ever growing data storage needs.  “A SAN is a dedicated configuration of multiple servers connected to peripheral storage devices using high-speed fiber and special  routers, switches, and hubs” (McData, 2001).  SANs enable the consolidation of data from disparate servers to be managed centrally on a storage network.  SANs offer key advantages over other storage solutions like NAS (Network Attached Storage) and DAS (Direct Attached Storage). Remote backup and recovery, increased uptime, more efficient data sharing and storage expansion are three key advantages in implementing a SAN.

A SAN is a specialized network that enables fast, reliable access among servers 

and external or independent storage resources. SANs use similar interconnect technologies as Local Area Networks (LANs) or Wide Area Networks (WANs) to  inter-connect its devices: routers, hubs, switches, and gateways.  SANs can be used to:

         Connect clustered servers for failover

         Interconnect mainframe and tape resources to distributed network servers

         Connect shared storage arrays

         Create parallel or alternate paths for high performance computing      environments.

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Enterprise management is now faced with the dilemma of storing critical data that is ever increasing and keeping it secure but available to multiple users, backing it up without driving up cost, and ensuring that the storage hardware and software are interoperable.  SANs reduce costs of storage resources, but the data on shared storage is potentially exposed to unauthorized access. There is “heightened concern about security and the ability to prevent unauthorized access to data, although security should be enforced and implemented in a SAN like any other network.


Until recently lack of industry standards posed a challenge to the security of SANs.  The Storage Network Industry Association (SNIA) Storage Security Industry Forum (SSIF) is now working towards “increasing the availability of robust storage security solutions” through a collaboration of storage vendors.


Network Attached Storage (NAS)

NAS solutions are typically configured as file-serving appliances accessed by  workstations and servers through TCP/IP (Transmission Control Protocol/Internet  Protocol) and applications such as NFS (Network File System) or CIFS (Common  Interface File System). NAS connections are mostly between workstation clients and the NAS file sharing facility.  The connections rely on the existing corporate network infrastructure to operate correctly.  NAS solutions are relatively easy to deploy, but have key performance constraints: network congestion of the existing LAN/WAN directly affects NAS performance.  Adding additional NAS components is easy, but accessing individual components as one entity is not possible because NAS components have unique identifiers.  Data backup in NAS usually cannot be centralized which limits it to direct-attached devices such as tape libraries or dedicated tape drives.  Key NAS strengths are it works well in environments where data is transferred over great distances and it works well for organizations that deliver file data to multiple clients over a network.


Direct Attached Storage

Direct Attached Storage is defined simply where each server has dedicated storage.   “Storage is seen and accessed by one host system and, should another host system need more storage that host will have to add more physical storage and perhaps I/O interfaces or host bus adapters.”

Typically, this setup incorporates different flavors of storage devices and poor storage utilization. Direct attached storage (DAS), in the form of independent drives, RAID arrays or tape libraries, is the most common storage architecture today.

DAS is the classical storage connecting concept, with which a memory unit is assigned to a server directly. DAS solutions are characterized by low costs, high data security and simple handling. DAS solutions offer great investment protection for already existing server environments.