Technology Guide: What is a SAN

What is a Storage Area Network

A SAN, or storage area network, is a dedicated network that is separate from LANs and WANs. It generally serves to interconnect the storage-related resources that are connected to one or more servers. It is often characterised by its high interconnection data rates (Gigabits/sec) between member storage peripherals and by its highly scalable architecture. Though typically spoken of in terms of hardware, SANs very often include specialised software for their management, monitoring and configuration.

SANs can provide many benefits. Centralising data storage operations and their management is certainly one of the chief reasons that SANs are being specified and deployed today. Administrating all of the storage resources in high-growth and mission-critical environments can be daunting and very expensive. SANs can dramatically reduce the management costs and complexity of these environments while providing significant technical advantages.

SAN Hardware

SANs are built up from unique hardware components. These components are configured together to form the physical SAN itself and usually include a variety of equipment. RAID storage systems, hubs, switches, bridges, servers, backup devices, interface cards and cabling all come together to form a storage system that provides the resources that facilitate the policies of an IT organisation.

It is very important to select the hardware devices (and their configuration) for a SAN with care and consideration. Many of the "standards" that are involved with SANs are concerned with interoperability. Some of these standards are still evolving and haven't been equally adopted by all manufacturers of equipment used in SANs. This can lead to difficulties when matching up devices from different vendors and suppliers. Since SANs are typically just as dependent upon software for their proper operation, it can be vital to secure the latest version information about software (and firmware) and potential compatibility issues.

RAID Systems

Most contemporary SANs include RAID systems as their primary data storage devices. These systems have become highly evolved and offer the foundation features that have come to be expected in a modern SAN. First and foremost, RAID systems offer data protection, or fault tolerance, in the event of a component or I/O path failure. This is true even if fundamental elements, such as disk drives, fail in the system. Additionally, by way of numerous data striping techniques (described below), and controller configurations, today's RAID systems offer very high performance, storage capacity, scalability, and survivability. Other reliability features available in today's RAID systems include redundant cooling systems, power supplies, controllers and even monitoring circuitry. These, and other features and characteristics, contribute dramatically to high data availability in a SAN. Modern RAID systems can even permit the direct connection of backup equipment, thus facilitating LAN-free and even serverless data backup and replication.

Background The roots of RAID technology can be traced back to 1987, when Patterson, Gibson and Katz at the University of California at Berkeley, published a paper entitled "A Case for Redundant Arrays of Inexpensive Disks (RAID) ". The ideas presented and explained in the paper involved combining multiple small, inexpensive disk drives into arrays in order to provide features that single drives alone couldn't supply. These new features centered around improving I/O performance and automatically preserving the contents of drives during, and after, drive or component failures.

Switches, Hubs and Bridges

More and more, the design and deployment of SAN technology involves incorporating specialised interconnection equipment. This category of devices often includes Fibre Channel Hubs, Switches and Bridges. This hardware is generally responsible for linking together the data storage peripherals, such as RAID systems, tape backup units and servers within a SAN.

These interconnection devices are somewhat analogous to their LAN-related counterparts. They perform functions such as data frame routing, media and interface conversion (i.e. copper to optical, Fibre Channel to SCSI), network expansion, bandwidth enhancement, zoning, and they allow concurrent data traffic. Just as customers today are more involved in the design and implementation of their LANs and WANs, they are also looking at these building blocks of SANs to create their own SAN solutions.

Backup Solutions

One of the most valuable time- and cost-saving features of a SAN architecture is its ability to offload backup operations from a LAN and/or backup servers. This capability can significantly increase the amount of LAN bandwidth available to network clients and end users during backup operations. When backup servers are relieved from the "data mover" role, they become more available for other productive tasks.

LAN-free and serverless backup solutions optimise backup operations by offloading backup data traffic from a LAN, thereby increasing the amount of LAN bandwidth available to end users. Serverless backup extends these performance gains by removing more than 90 percent of the backup administration overhead that is usually placed on a backup server as backups are performed. This is achieved by incorporating some of the backup intelligence into the data storage or connectivity peripherals themselves. This can significantly free up backup servers by releasing them from large portions of a backup operation's administration and data moving chores. Using these SAN based backup solutions lets administrators optimise network and server utilisation.

SAN Software

More than ever before, software is playing a vital role in the successful deployment of SANs. Much of the technology, and many of the features, provided by SANs are actually embedded in its software. From volume management to serverless backup, choosing and configuring the software components is very important and should be done with care.

Many companies offer a wide variety of software products and solutions that are specifically designed to enhance the performance, data availability and manageability of SANs. Some of these solutions have been custom developed by these companies for lines of data storage systems. Other offerings are more universal or "open" and address a very broad range of customer requirements and equipment.

SAN Management Software

SANs today can become rather complex in both their design and implementation. Adding to this are issues relating to their configuration, resource allocation and monitoring. These tasks and concerns have led to a need to proactively manage SANs, their client servers and their combined resources. These needs have led to this new category of software that has been specifically developed to perform these functions and more. Though somewhat recent in its development, SAN management software borrows heavily from the ideas, functions and benefits that are mature and available for traditional LANs and WANs.

Ideally, SAN management software would be universal and work with any SAN. But in today's multi-vendor and hardware-diverse SAN environments, this management software is often proprietary or tied to certain products and vendors. While this is beginning to change, it still means that SAN management software must be selected with great care, and consideration given to the SAN equipment manufacturers, OS platforms, firmware revisions, HBA drivers, client applications, and even other software that may be running on the SAN. Until such time as SAN management software becomes very universal, it will be quite important, and even vital, to work closely with product providers in order to achieve the best results in obtaining SAN management goals and benefits.When selecting SAN management software, it is particularly important to ask lots of questions. Inquire about supported OS platforms, compatibility issues with other vendors, minimum revision levels of the components that are (or will be) in the SAN, and any feature restrictions that may be imposed in certain environments.

Server Clustering

In a SAN context, server clustering generally refers to the grouping together of servers for the purpose of enhancing their performance and/or providing failover protection in the event that a member server malfunctions. Uninterrupted and seamless availability of data and applications during and after a server failure is a primary benefit of a server cluster architecture within a SAN.

Though servers can be clustered together outside of a SAN environment, there are many benefits associated with clustering them together as part of a SAN. These benefits include shared access to resilient disk and tape backup systems, higher performance data replication options, improved storage scalability, and enhanced resource availability through the inherent advantages of SAN based storage systems.

In many cases, the specialised software involved in server clustering can even fail back a server in the event it is repaired or begins working properly again. Other software options can even divide application tasks among servers in a cluster in order to dramatically improve its response time and performance.

Data Replication

Data Replication provides many benefits in today's IT environments. For example, it can enable system administrators to create and manage multiple copies of business-critical information across a global enterprise. This can maximise business continuity, enabling disaster recovery solutions, Internet distribution of file server content, and improve host processing efficiency by moving data sets onto secondary servers for backup operations. These applications of data replication are frequently enhanced by the inherent "high data availability" features provided by today's SAN architectures.

Copying data from one server to another, or from one data storage system to one or more others, may be achieved in a number of ways. Traditionally, organizations have used tape-based technologies to distribute information. However, for many organizations that have built their businesses on an information infrastructure, the demand for instant access to information is increasing. While tape-based disaster recovery and content distribution solutions are robust, they do not support an instant information access model. Many organizations are supplementing, or replacing, their existing disaster recovery and content distribution solutions with online replication.

Volume and File Management

One of the many useful, and often touted, features of most SANs is their easy and inherent scalability. And while it is true that SAN technology makes adding physical devices fairly simple, it is important to understand that merely adding raw hardware resources to a SAN doesn't mean that its clients and their operating systems, or other SAN members, will automatically recognize them. This is particularly true when it comes to adding disk storage capacity.

Most SANs incorporate some type of data storage hardware. Generally, this equipment is in the form of RAID storage systems and JBODs. Adding additional, or higher capacity, disk drives to these RAID and JBOD systems in a SAN is a very common way to increase the SAN's raw storage capacity. And, while the RAID systems will often auto detect these additional disk drives, they won't typically expand the file systems that were created on them before the additional disk capacity was added. In fact, most of a SAN's client servers and their operating systems will not automatically do anything about the extra added capacity. The simple reason for this is that while the 'raw' storage capacity was increased by adding additional hardware (disk drives), the file systems that existed on the storage systems - before the additional disks where added - won't magically expand to include the new disk space without some help from specialised volume and file management software. This is especially true when expanding JBODs.

Importance of Storage

Storage was once a peripheral – a mere feature of the server. Those days are long gone, and that's a good thing because information shouldn't always be hidden behind, or bottled up inside a single server. It should be positioned so that it can be made quickly but securely available to other applications and/or departments within the enterprise. So, now that storage is out from behind the server's shadow, we need to recognize its true value. Here's why:

The value of data as a corporate asset has risen dramatically over the last few years. Maintaining its availability, integrity and security is a now matter of life or death for many enterprises.

With the advent of storage networking, data storage as an enterprise core competency has become demanding and complex. And with new technologies reaching the market at a torrid pace, it becomes harder and harder to understand and make judgments about all the alternatives.

There is currently a critical shortage of the trained staff required to manage the new enterprise storage environment. As a result, expertise in recruiting, training and retaining storage management staff is now a vital enterprise IT function.

The value of data

Data – translated by applications and infrastructure into information – has grown in value to the point where, for many enterprises, it is the most valuable corporate asset. It's a competitive differentiator – the underpinning of all customer-facing applications like CRM and CSM. And with the advent of the Web, it has expanded in importance to become mission-critical to the very enterprise as viewed through the portal. In this environment, storage is now the single most important IT resource for assuring:

Data availability – the persistent availability of data as defined by the storage utility model which basically assures that enterprise data will always be accessible, will always be "on" – just like electricity. Lost access to data can be severely damaging and possibly fatal to the enterprise. For example, in a health care setting, continuous access to data could make the difference between life and death.

Data integrity – the protection and preservation of data from corruption, loss and outside attack. Storage can also be thought of as a vault. When you retrieve data, you expect to retrieve exactly what was deposited. Storage and storage management personnel are the guardians of data.

Disaster recoverability – the ability of storage networks and storage management applications to play a critical role in recovering from the inevitable disaster. Disaster scenarios include anything from the loss of a server running a critical application, to the loss of an entire data center due to fire, flood, earthquake, etc.

An enterprise core competency

It would be a gross oversimplification to say that storage was once a simple matter of plugging an array into a SCSI port. Then again, compared to the array of alternatives available now from FC-AL to FC Fabric, the IP derivatives and soon InfiniBand and beyond, the days of one-size-fits-all SCSI are also long gone. Data storage as an enterprise core competency is becoming exceeding complex. Here's a brief, and by no means exhaustive, list of the technologies now directly involved in or significantly touching upon data storage:

Fibre Channel Arbitrated Loop and fabric architectures
Ethernet and IP
Server clustering
Data backup and restoration
SCSI
Wide- and metropolitan-area networking protocols
Bridging, routing and switching
Host bus adapters and drivers
Broadband communications
Enterprise management applications
Database and file system architectures
Operating systems

Growing storage staff

There are benefits to be realized today from implementing storage networks, but because of the shortage of IT personnel with storage expertise, enterprises are hesitant to move forward. Recruiting, training and retaining skilled storage management staff must become a core IT competency if the real benefits from storage innovation are to be realized.

Conclusion

The nature of the storage environment has changed radically in the last few years. It is it now characterized by unprecedented growth in the volume of data to be managed and a quantum leap in complexity and the sheer number of available combinations and permutations. Add to that the growing value of data to the enterprise, and the overwhelming importance of storage and storage networking becomes obvious.

A to Z of Storage Terms

ACCESS CONTROL: General term for a group of security techniques such as using passwords or smart cards to limit access to a computer or network only to authorized users.

AVAILABILITY: The accessibility of a computer system or network resource.

BACKUP/RESTORE: The act of copying files and databases to protect them in the event of a system failure or similar catastrophe and retrieving them at a later date.

BBU (Battery Backup Unit): A battery-operated power supply used as an auxiliary source of electricity in the event of power failure. The battery guarantees no lost writes and orderly transitions or shutdowns during power outages.

BCV (Business Continuance Volumes): Business Continuance Volumes are copies of active production volumes that can be used to run simultaneous tasks in parallel with one another. This gives customers the ability to do concurrent operations, such as data warehouse loads and refreshes or point-in-time backups, without affecting production systems.

BUS: A transmission channel in a computer or on a network that carries signals to and from devices attached to the channel.

BUSINESS CONTINUANCE: The technique of ensuring that a business is able to weather a natural or man-made catastrophe through the deployment of fault-tolerant and redundant hardware and software systems.

CACHING: A method of temporarily storing frequently accessed data in RAM or an special area of a hard disk drive, to speed processing. With sufficient storage-processor and backup memory, a storage system also supports write caching temporary storage where data is held for a short time before being written on disk for permanent storage.

CHANNEL: A high bandwidth connection between a processor and other processors or devices.

CHECKSUM: A number of bits that is transmitted with data so that the receiving device can verify the accuracy of the data that it received. If the number of bits that arrives is the same that is sent, the transmission is believed to be complete.

CLUSTER: A collection of high-performance, interconnected computer servers working together as a single processing resource in an application environment to provide scalable, high availability to both users and applications.

CONNECTIVITY: The ability of hardware devices or software to communicate with other hardware or software.

CROSS-PLATFORM: Systems that are operating-system independent and can operate across different system platforms.

DATA INTEGRITY: The accuracy of data after being transmitted or processed.

DATA MART: A repository of data, often a scale-down data warehouse, usually tailored to the needs of a specific group within an organization

DATA MINING: Using advanced statistical tools to identify commercially useful patterns in databases.

DATA WAREHOUSE: A very large repository of data comprising nearly all of a company’s information.

DEBUG: To detect, locate, and correct problems in a program or malfunctions in software. (Troubleshoot in a hardware context.)

DEFRAG: To improve file access by rearranging data so that whole files are stored in contiguous sectors on a hard disk.

DEVICE: A computer subsystem such as a printer, serial port, disk drive, or video adapter. Frequently, devices require their own controlling software (device drivers) to communicate with the computer system.

DISASTER RECOVERY: Preventative measures using redundant hardware, software, data centers and other facilities to ensure that a business can continue operations during a natural or man-made disaster and if not, to restore business operations as quickly as possible when the calamity has passed.

DISK CONTROLLER: The hardware that controls the writing and reading data to and from and to a disk drive. It can be used with floppy disks or hard drives. It can be hard-wired or built into a plug-in interface board.

DISK MIRRORING: Disk mirroring provides the highest data availability for mission-critical applications by creating two copies of data on separate disk drives. The technique ensures both the highest availability and highest system performance.

DISK STRIPING: Combining a set of same-size disk partitions from 2 to 32 separate disks into a single volume that virtually "stripes" these disks in a way that the operating system recognizes as a single drive. Disk striping enhances performance by enabling multiple I/O operations in the same volume to proceed simultaneously.

DISK STRIPING with PARITY: Preserving parity information across a disk stripe so that if one disk partition fails, its data can be re-created with information stored across the remaining portions of the disk stripe.

E-INFOSTRUCTURE: A shared foundation of technologies, tools, services, and intellectual capital that enables an uninterrupted flow of information

EMC PROVEN E-INFOSTRUCTURE: An EMC program that recognizes leading corporations that operate in the 24-hour Internet workday and that adhere to the highest levels of information availability and customer satisfaction.

ENTERPRISE STORAGE: A combination of intelligent storage systems, software and services. Together, these products and services enable an enterprise to store, retrieve, manage, protect and share information from all major computing environments, including UNIX, Windows 2000 and mainframe platforms

ERROR CORRECTION CODING (ECC): An encoding method that detects and corrects errors at the receiving end of data transmission. ECC is used by most modems.

ESN (Enterprise Storage Network): It’s a specialized, open network that is designed to offer universal data access for every major computing platform, operating system, and application in the world across any combination of SCSI, Ultra SCSI, Fibre Channel, and ESCON® technologies. It integrates Symmetrix Enterprise Storage systems, EMC Connectrix, advanced, highly resilient network technology, and enterprise storage software with consulting and services into one complete package. An EMC ESN enables corporations to accelerate data access, boost network performance, automate storage management, and fully exploit the power of information regardless of its location.

FABRIC: A Fibre Channel topology with one or more switching devices.

FAILOVER: Data is immediately and nondisruptively routed to an alternate data path or device in the event of an event of an adapter, cable, channel controller or other device.

FAST DUMP/RESTORE (FDR): A family of mainframe-based backup/restore utilities that use Symmetrix with existing mainframe infrastructures to provide a comprehensive suite of fast, nondisruptive information protection solutions for both mainframe and open systems environments.

FAULT TOLERANCE: A computer or operating system’s ability to respond to a catastrophic event like a power outage or hardware failure so that no data is lost or corrupted.

FIBREALLIANCE: The FibreAlliance (www.fibre alliance.org) is an open association of industry-leading Fibre Channel vendors committed to accelerating the adoption rate of storage area networks (SANs). Members are working to develop a framework specification within which multiple vendors can develop integrated management environments for enterprise SAN customers.

FIBER CHANNEL ARBITRATED LOOP (FC-AL): FC-AL places up to 126 devices on a loop to share bandwidth. Typically, this is done using a star layout that is logically a loop, employing a Fibre Channel hub. This allows IT managers to add or remove devices without having to bring the entire loop down.

FIBRE CHANNEL (FC): Fibre channel is nominally a one-gigabit-per-second data transfer interface technology, although the specification allows data transfer rates from 133 megabits per second up to 4.25 gigabits per second. Data can be transmitted and received at one-gigabit-per-second simultaneously. Common transport protocols, such as Internet Protocol (IP) and Small Computer System Interface (SCSI), run over Fibre Channel. Consequently, high-speed I/O and networking can stem from a single connectivity technology.

HARD DISK: A mass storage device for computer data that consists of a hermetically sealed enclosure that holds stacked, rotating, magnetizable disks accessed by multiple read/write heads.

HARDWARE RAID: Dual-storage processors that improve data availability and performance create data protection information and transfer it to the disk drives. They are located in an external storage subsystem, freeing the CPU from performing RAID parity, striping, and rebuild overhead calculations. This intelligent circuit board controls the disk drives.

HBA (Host Bus Adapter): An SCSI-2 adapter that plugs into a host and lets the host communicate with a device. The HBA usually performs the lower level of the SCSI protocol and normally operates in the initiator role.

HOST: A computer server, typically networked, that runs applications used by or from other computers (e.g., web servers, file servers, and application servers).

HOT SPARE: In RAID systems, a spare drive in the disk array that is configured as a backup for rebuilding data in the event another drive fails.

HOT SWAPPING: The process of removing and replacing a failed system component while the system remains online.

HUB: A device joining communications lines at a central location, providing a common connection to all devices on the network.

INFORMATION MANAGEMENT: The entire process of defining, evaluating, protecting, and distributing data within an organization.

INFRASTRUCTURE: The basic, fundamental architecture of a computer system. The infrastructure determines how the system functions and how flexible it is in meeting future demands.

INTELLIGENT: A device is intelligent when it is controlled by one or more processors integral to the device.

ISA (Intelligent Storage Architecture): EMC's Intelligent Storage Architecture consolidates information management functions including backup/restore, disaster recovery, migration, and information sharing into a single enterprise storage system. This provides a single consistent platform from which to manage, access, and share information.

INTEROPERABILITY: The ability of hardware and software made by a variety of different manufacturers to work seamlessly together.

JBOD (Just a Bunch of Disks): A group of hard disks, usually without intelligence (processors).

LINK: A connection between two Fibre Channel ports.

LUN (Logical Unit Number): An encoded 3-bit identifier used on an SCSI bus to distinguish among up to eight devices (logical units) with the same SCSI ID. An LUN is an indivisible unit presented by a storage device to its host. LUNs are assigned to each disk drive in an array so the host can address and access the data on those devices.

LUN Masking: An array security feature that lets a server access only its own and no other LUNs on a Fibre Channel. Each LUN can specify what host or combination of hosts has access to that LUN.

MAINFRAME: A computer primarily used by Global 2000 corporations for large-scale commercial applications. A mainframe is capable of supporting many users from many terminals.

MODULARITY: An approach to developing hardware or software that breaks projects into smaller units (or modules) that are deliberately designed as standalone units that can work with other sections of the program. The same module can perform the same task in another or several other programs or components. Modifying the way that module works will have no adverse affects on the other components of a program.

MULTIPATHING: Multipathing allows for two or more data paths to be simultaneously used for read/write operations, enhancing performance by automatically and equally dispersing data access across all the available paths.

NAME SERVICES LOGIN: Worldwide-exclusive names that allow a device to log into the switch.

NONVOLATILE: Data in memory, cache and other electronic repositories are protected by a battery backup system to prevent their loss in the event of a power failure.

OLTP: Online Transaction Processing is a system that processes transactions the instant the computer receives them and updates master files immediately. OLTP is essential for good financial record keeping and inventory tracking.

PARITY: A data-error-checking procedure where the number of 1s must always be the same—either even or odd— for each group of bits submitted without error. Parity information is saved and compared with each subsequent calculations of whether the number is odd or even.

PARITY BIT: An extra bit used in checking for errors in transferred groups of data bits. In modem communications, it is used to check the accuracy of each transmitted character. In RAM, a parity bit is used to check the accuracy with which each byte is stored.

PB (PetaByte): 1 quadrillion bytes or one thousand terabytes.

PORT: On a computer, it is a physical connecting point to which a device is attached.

PROTOCOL: A set of rules or standards intended to enable computers to communicate.

RAID (Redundant Array of Independent Disks): Data is stored on multiple magnetic or optical disk drives to increase output performance and storage capacities and to provide varying degrees of redundancy and fault tolerance. Instead of storing valuable data on a single hard disk that could fail at any time, RAID makes sure a backup copy of all information always exists by spreading data among multiple hard disks.

RAID Levels: Different levels offer trade-offs among speed, reliability, and cost.

Level 0 is disk striping only for better performance. Its data transfer and I/O rates are very high, but it provides no safeguards against data failure.

Level 1 uses disk mirroring. All data is duplicated on two drives, offering the highest data reliability. Its data transfer rate is higher than single disk for read and similar for write. Its I/O rate is twice that of single disk for read but similar for write.

Level 1/0 is a combination of Levels 1 and 2, mirroring and striping. It offers the same data reliability as RAID 1. Its data-transfer and I/O rates are very high, but slower than RAID 0 for writes

Level 3 stripes data across three or more drives. All drives operate in parallel to achieve the highest data transfer rate. Parity bits are stored on separate, dedicated drives. Its I/O rate is similar to single disk.

Level 5 is the most widely used. Data is striped across three or more drives for high performance. The parity bits from two drives are stored on a third drive. Its data reliability is similar to RAID 3. Its data transfer and I/O rates are very high for read, but slower than single disk for write.

READ-ONLY: Data can be retrieved (read) but not altered (written).

REDUNDANT: Backup arrays, drives, disks or power supplies that duplicate functions performed elsewhere.

ROBUST: Able to function or continue to function well in a variety of unanticipated situations.

SCALABILITY: The capacity of hardware, software and networks to change size according to the number of users that they accommodate. Most often, scalability refers to the capacity to expand rather than shrink.

SCSI: Small Computer System Interface. The standard set of protocols for host computers communicating with attached peripherals. SCSI allows connection to as many as six peripherals including printers, scanners, hard drives, zip drives, and CD-ROM drives.

SCSI-2: An enhanced ANSI standard for SCSI standard for SCSI buses. It offers increased data width, increased speed, or both.

SCSI bus: A parallel bus that carries data and control signals from SCSI devices to an SCSI controller.

SOFTWARE RAID: Uses the server processor to perform RAID calculations. Host CPU cycles that read and write data from and to disk are taken away from applications. Software RAID is less costly than dedicated hardware RAID storage processors, but its data protection is less efficient and reliable.

SWITCH: A network device that selects a path or circuit for sending a data between destinations.

TERABYTE (TB): A thousand billion bytes or one thousand gigabytes.

THROUGHPUT: In computers, it is a measurement of the amount of work that can be processed within a set time period. In networking, it is a measurement of the amount of data that can be successfully transferred with a set time period.

VOLUME: A virtual disk into which a file system, database management system or other application places data. A volume can be a single disk partition or multiple partitions on one or more physical drives.

WORKLOAD BALANCING: It’s a technique that ensures no one data path can become overloaded while others have underutilized bandwidth causing an I/O bottleneck. When one or more paths become busier than others, I/O traffic shifts from the busy paths to the others, further enhancing throughput over the already efficient multipathing method.

WRITE-CACHE: A form of temporary storage in which data is stored (or cached) in memory before being written to a hard disk for permanent storage. Caching enhances overall system performance by decreasing the number of times the central processor reads and writes to a hard disk.

WRITE-MODE: The state in which a program can write (record) information in a file. In the write-mode, the user is permitted to make changes in existing information.

ZONING: Several devices are grouped by function or by location. All devices connected to a connectivity product may include configuration of one or more zones. Devices in the same zone can see each other; devices in different zones cannot.

Updated on July 23, 2002

Technology Guide: What is a SAN

Contents

The value of data

An enterprise core competency

Growing storage staff

Conclusion