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Encyclopedia > Storage area network

In computing, a storage area network (SAN) is an architecture to attach remote computer storage devices such as disk array controllers, tape libraries and CD arrays to servers in such a way that to the operating system the devices appear as locally attached devices. Although cost and complexity is dropping, as of 2007, SANs are still uncommon outside larger enterprises. Memory (Random Access Memory) Look up computing in Wiktionary, the free dictionary. ... In computing, a disk array controller is a computer hardware device which provides secondary storage services to computer systems, often in large servers. ... A tape silo being loaded. ... This article or section does not cite its references or sources. ... 2007 is a common year starting on Monday of the Gregorian calendar. ... Enterprise storage is the field of information technology focused on the storage, protection, and retrieval of data in large-scale environments. ...


(By contrast to a SAN, network attached storage (NAS), uses file-based protocols such as NFS or SMB/CIFS where it is clear that the storage is remote, and computers request a portion of an abstract file rather than a disk block.) Network-attached storage (NAS) systems are generally computing-storage devices that can be accessed over a computer network, rather than directly being connected to the computer (via a computer bus). ... Network File System (NFS), a protocol originally developed by Sun Microsystems in 1984 and defined in RFCs 1094, 1813, and 3530 (obsoletes 3010) as a distributed file system, allows a user on a client computer to access files over a network as easily as if attached to its local disks. ... Server message block (SMB) is a network protocol mainly applied to share files, printers, serial ports, and miscellaneous communications between nodes on a network. ...

Contents

Network types

Most storage networks use the SCSI protocol for communication between servers and disk drive devices, though they do not use its low-level physical interface, instead using a mapping layer such as the FCP mapping standard. This article does not cite its references or sources. ... This article or section does not cite its references or sources. ...

This article or section does not adequately cite its references or sources. ... . The initial letter is shown capitalized due to technical restrictions. ... The Internet protocol suite is the set of communications protocols that implement the protocol stack on which the Internet runs. ... In computer science, HyperSCSI is a network protocol for sending and receiving SCSI commands. ... Ethernet is a large, diverse family of frame-based computer networking technologies that operates at many speeds for local area networks (LANs). ... ATA over Ethernet (AoE) is a network protocol developed by Coraid, Inc. ... Ethernet is a large, diverse family of frame-based computer networking technologies that operates at many speeds for local area networks (LANs). ...

Benefits

Sharing storage usually simplifies storage administration and adds flexibility since cables and storage devices do not have to be physically moved to move storage from one server to another. Note, though, that with the exception of SAN file systems and clustered computing, SAN storage is still a one-to-one relationship. That is, each device, or Logical Unit Number (LUN) on the SAN is "owned" by a single computer (or initiator). In contrast, Network Attached Storage (NAS) allows many computers to access the same set of files over a network. The contrast between the SAN and NAS has been blurred with the creation of a NAS head. The SAN File System, also known as SFS, is distributed file system software created by DataPlow that enables high-speed, cluster file sharing among multiple, storage area network (SAN)-attached computers. ... Linux Cluster at Purdue University A computer cluster is a group of locally connected computers that work together as a unit. ... In computer storage, a logical unit number or LUN is an address for an individual disk drive and by extension, the disk device itself. ... Samba Network Icon Network-attached storage (NAS) is the name given to dedicated data storage technology that can be connected directly to a computer network to provide centralized data access and storage to heterogeneous network clients. ... Samba Network Icon Network-attached storage (NAS) is the name given to dedicated data storage technology that can be connected directly to a computer network to provide centralized data access and storage to heterogeneous network clients. ...


SANs tend to increase storage capacity utilization, since multiple servers can share the same growth reserve.


Other benefits include the ability to allow servers to boot from the SAN itself. This allows for a quick and easy replacement of faulty servers since the SAN can be reconfigured so that a replacement server can use the LUN of the faulty server. This process can take as little as half an hour and is a relatively new idea being pioneered in newer data centers. There are a number of emerging products designed to facilitate and speed up this process still further. For example, Brocade Communication Systems offers an Application Resource Manager product which automatically provisions servers to boot off a SAN, with typical-case load times measured in minutes. While this area of technology is still new, many view it as being the future of the enterprise datacenter. A data center is a facility used for housing a large amount of electronic equipment, typically computers and communications equipment. ...


SANs also tend to enable more effective disaster recovery processes. A SAN attached storage array can replicate data belonging to many servers to a secondary storage array. This secondary array can be local or, more typically, remote. The goal of disaster recovery is to place copies of data outside the radius of effect of an anticipated threat, and so the long-distance transport capabilities of SAN protocols such as Fibre Channel and FCIP are required to support these solutions. (The physical layer options for the traditional direct-attached SCSI model could only support a few meters of distance: not nearly enough to ensure business continuance in a disaster.) Demand for this SAN application has increased dramatically after the September 11th attacks in the United States, and increased regulatory requirements associated with Sarbanes-Oxley and similar legislation. For other uses, see DRP (disambiguation). ... Fibre Channel over IP (FCIP or FC/IP, also known as Fibre Channel tunneling or storage tunneling), is an Internet Protocol (IP)-based storage networking technology developed by the Internet Engineering Task Force (IETF). ... A sequential look at United Flight 175 crashing into the south tower of the World Trade Center The September 11, 2001 attacks (often referred to as 9/11—pronounced nine eleven or nine one one) consisted of a series of coordinated terrorist[1] suicide attacks upon the United States, predominantly... Before the signing ceremony of the Sarbanes-Oxley Act, President George W. Bush meets with Senator Paul Sarbanes, Secretary of Labor Elaine Chao and other dignitaries in the Blue Room at the White House July 30, 2002. ...


Newer SANs allow duplication functionality such as "cloning", "Business Continuance Volumes (BCV)" and "snapshotting," which allows for real-time duplication of LUN, for the purposes of backup, disaster recovery, or system duplication. With higher-end database systems, this can occur without downtime, and is geographically independent, primarily being limited by available bandwidth and storage. Cloning and BCV's create a complete replica of the LUN in the background (consuming I/O resources in the process), while snapshotting stores only the original states of any blocks that get changed after the "snapshot" (also known as the delta blocks) from the original LUN, and does not significantly slow the system. In time, however, snapshots can grow to be as large as the original system, and are normally only recommended for temporary storage. The two types of duplication are otherwise identical, and a cloned or snapshotted LUN can be mounted on another system for execution, or backup to tape or other device, or for replication to a distant point.


Disk controllers

The driving force for the SAN market in the enterprise space is rapid growth of highly transactional data that require high speed block level access to the hard drives (such as data from email servers, databases, and high usage file servers). Historically, enterprises would have "islands" of high performance SCSI storage RAIDs that were locally attached to each application server. These "islands" would be backed up over the network, and when the application data exceeded the maximum amount of data storable by the individual server, the end user would often have to upgrade his server to keep up.


The disk controllers used in enterprise SAN environments are designed to provide applications with block level access to high speed, reliable "virtual hard drives" (or LUNs). In addition, modern SANs allow enterprises to intermix FC SATA drives with their FC SCSI drives. Some studies indicate that SATA drives have lower performance, a higher failure rate, higher capacity, and lower prices than SCSI[citation needed]. This allows enterprises to have multiple tiers of data that will migrate over time to different types of media. For example: many enterprises relegate files that are rarely accessed to FC SATA while keeping their frequently used data in FC SCSI. The disk controller (or hard disk controller) is the circuit which allows the CPU to communicate with a hard disk, floppy disk or other kind of disk drive. ... A SATA power connector. ...


Another feature of most enterprise disk controllers is an I/O cache. This feature allows higher overall performance for writing to the controller, and in some cases (like for contiguous file access where read ahead is enabled) reading from the controller.


SAN types

SANs require an infrastructure specially designed to handle storage communications called a fabric. Thus, they tend to provide faster and more reliable access than higher level protocols such as NAS. A fabric is similar in concept to a segment in a local area network. Switched Fabric is a Fibre Channel topology where many devices connect with each other via Fibre Channel switches. ... Samba Network Icon Network-attached storage (NAS) is the name given to dedicated data storage technology that can be connected directly to a computer network to provide centralized data access and storage to heterogeneous network clients. ... Fabric may mean: Cloth, a flexible artificial material made up of a network of natural or artificial fibres Fabric (club), a London dance club Fibre Channel fabric, a network of Fibre Channel devices enabled by a Fibre Channel switch using the FC-SW topology This is a disambiguation page, a...


The industry standard SAN technology is Fibre Channel networking with the SCSI command set. A typical Fibre Channel SAN fabric is made up of a number of Fibre Channel switches. Today, all major SAN equipment vendors also offer some form of Fibre Channel routing solution, and these bring substantial scalability benefits to the SAN architecture by allowing data to cross between different fabrics without merging them. These offerings use proprietary protocol elements, and the top-level architectures being promoted are radically different. When extending Fibre Channel over long distances for disaster recovery solutions, it can be mapped over other protocols. For example, products exist to map Fibre Channel over IP (FCIP) and over SONET/SDH. It can also be extended natively using signal repeaters, high-power laser media, or multiplexers such as DWDMs. This article or section does not adequately cite its references or sources. ... This article does not cite its references or sources. ... A Fibre Channel switch is a computer storage device that allows the creation of a Fibre Channel fabric. ...


Types of SAN

A centralized storage area network contains many heterogeneous servers connected to one single storage space. The single storage space can have heterogeneous storage entities or disk drives. Centralized storage area networks are useful for simplifying the storage architecture in large organizations. The storage space can be treated as a black box so that administration of storage is easy. Centralized storage area networks are compatible with many heterogeneous server environments including Unix, HPUX, Solaris, Linux, Windows based servers and more. This article or section does not cite its references or sources. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®) is a computer operating system originally developed in the 1960s and 1970s by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ... HP-UX is Hewlett-Packards proprietary implementation of the Unix operating system. ... Look up Solaris in Wiktionary, the free dictionary. ... Linux (IPA pronunciation: ) is a Unix-like computer operating system family. ... Microsoft Windows is the name of several families of proprietary software operating systems by Microsoft. ...


A distributed storage area network contains many geographically-dispersed disk drive networks. All the networks are treated as one unit and are connected by the iSCSI storage area network protocol. Distributed storage area networks is a sub-network of shared storage devices that allows for all information stored to be shared among all of the servers on the network. Distributed storage area networks are most popular in large organizations with geographically dispersed storage pools, that can be connected and communicated through iSCSI. Disk Drive is the afternoon show on CBC Radio Two. ... This article or section is in need of attention from an expert on the subject. ... In the field of telecommunications, a communications protocol is the set of standard rules for data representation, signalling, authentication and error detection required to send information over a communications channel. ...


SAN vs Traditional Server Based Storage

In a typical large LAN-installation, each of a number of servers (and perhaps mainframes) may have its own dedicated storage devices. If a client needs access to a particular storage device, it must go through the server that controls the device. In a SAN, no server sits between the storage devices and the network; instead, the storage devices and servers are linked directly to the network. The SAN arrangement improves client-to-storage access efficiency, as well as direct storage-to-storage communications for backup and replication functions.[1]


Compatibility

One of the early problems with Fibre Channel SANs was that the switches and other hardware from different manufacturers were not entirely compatible. Although the basic storage protocols (such as FCP) were always quite standard, some of the higher-level functions did not interoperate well. Similarly, many host operating systems would react badly to other Operating Systems sharing the same fabric. Many systems were pushed to the market before standards were finalized and vendors innovated around the standards. Fibre Channel is a serial computer bus intended for connecting high speed storage devices to computers. ... An operating system (OS) is a set of computer programs that manage the hardware and software resources of a computer. ...


The combined efforts of the members of the Storage Networking Industry Association (SNIA) improved the situation during 2002 and 2003. Today most vendor devices, from HBAs to switches and arrays, interoperate nicely, though there are still many high-level functions that do not work between different manufacturers' hardware. The Storage Networking Industry Association, or SNIA, was incorporated in December, 1997, and is a registered 501-C6 non-profit trade association. ... Host Bus Adapter (Fibre Channel) Host Bus Adapter (SCSI) In computer hardware, a host adapter or host bus adapter (HBA) connects a host system (the computer) to other network and storage devices. ...


SANs at work

SANs are primarily used in large scale, high performance enterprise storage operations. It would be unusual to find a Fibre Channel disk drive connected directly to a SAN. Instead, SANs are normally networks of large disk arrays. SAN equipment is relatively expensive, therefore, Fibre Channel host bus adapters are rare in desktop computers. The iSCSI SAN technology is expected to eventually produce cheap SANs, but it is unlikely that this technology will be used outside the enterprise data center environment. Desktop clients are expected to continue using NAS protocols such as CIFS and NFS. The exception to this may be remote replication sites. Remote replication enables the data center environment to exist in multiple locations for disaster recovery and business continuity purposes. Enterprise storage is the field of information technology focused on the storage, protection, and retrieval of data in large-scale environments. ... Disk Drive is the afternoon show on CBC Radio Two. ... Hewlett-Packard Disk-Arrays: HASS (top) and NIKE (OEMd Data General SCSI Clariion) EMC CLARiiON CX500 (Cover removed on one Shelf) EMC Symmetrix DMX1000 A disk array is an enterprise storage system which contains multiple disk drives. ... A data center is a facility used for housing a large amount of electronic equipment, typically computers and communications equipment. ...


SANs in a Small Office / Home Office (SOHO)

With the increasing rise of digital media in all phases of life and its effect on storage needs, it's natural that SANs have begun to enter into the SOHO market. Historically, this market was dominated by NAS systems, but SOHO is poised to become a major market for SAN infrastructure as SOHO performance requirements rise. The modern concept of Small Office and Home Office or SoHo, or Small or Home Office deals with the category of business which can be from 1 to 10 workers. ... Samba Network Icon Network-attached storage (NAS) is the name given to dedicated data storage technology that can be connected directly to a computer network to provide centralized data access and storage to heterogeneous network clients. ...


Systems such as film scanners and video editing applications require performance that cannot be provided by traditional file servers. For example, motion picture film at 2048x1536 requires more than 300MBytes/s for each real-time stream, and several of these streams can be required simultaneously. As a result, several Gigabits per second can be required, which creates a problem for standard NAS technologies. In addition, these systems need to work with the same files collaboratively, so they cannot be distributed through different file servers or DAS connections. Direct Attached Storage (DAS) refers to a digital storage system directly attached to a server or workstation, without a storage network in between. ...


Instead of having many computers connected to the network, with each one requiring a low bandwidth and only the server being stressed under heavy traffic, the SOHO "real-time" area only needs to integrate a few systems, but all of them require high bandwidth to access the same files. These problems are addressed very well by 4Gbit Fibre Channel SAN infrastructures, where the aggregated bandwidth for sequential I/O operations is extremely high.


Storage virtualization and SANs

  • Storage virtualization refers to the process of completely abstracting logical storage from physical storage. The physical storage resources are aggregated into storage pools, from which the logical storage is created. With storage virtualization, multiple independent storage devices, that may be scattered over a network, appear to be a single monolithic storage device, which can be managed centrally. Storage Virtualization is commonly used in SANs. Virtualization of storage helps achieve location independence by abstracting the physical location of the data. The Virtualization system presents to the user a logical space for data storage and itself handles the process of mapping it to the actual physical location.

White papers: Storage Virtualization refers to the process of completely abstracting logical storage from physical storage. ...

  • whitepapers.techrepublic.com

Virtualization software: product descriptions and specifications

  • Overview Article and Product Specifications on Storage Virtualization Software from a number of vendors [1]

See also

ATA over Ethernet (AoE) is a network protocol developed by Coraid, Inc. ... This article or section does not adequately cite its references or sources. ... File Area Networking refers to various methods of sharing files over a network such as storage devices connected to a file server or Network-attached storage. ... A file hosting service or online file storage service is an Internet hosting service specifically designed to host static content, typically large files that are not web pages. ... InfiniBand is a switched fabric communications link primarily used in high-performance computing. ... . The initial letter is shown capitalized due to technical restrictions. ... Compellent SAN Winslow Technologies SAN Solutions Computer Associates BrighStor SAN Manager Enterprise Fabric Connectivity (EFC) Manager EMC VisualSAN HP OpenView Storage Area Manager Sun StorEdge Enterprise Storage Manager (ESM) Veritas software SANPoint Control IBM TotalStorage SAN Volume Controller Onaro SANscreen SAN Service Management See also Storage Resource Manager Category: ... Samba Network Icon Network-attached storage (NAS) is the name given to dedicated data storage technology that can be connected directly to a computer network to provide centralized data access and storage to heterogeneous network clients. ... In computing, a redundant array of inexpensive disks, also later known as redundant array of independent disks (commonly abbreviated RAID) is a system which uses multiple hard drives to share or replicate data among the drives. ... SMI-S, or the Storage Management Initiative Specification, is a storage standard ratified by the Storage Networking Industry Association (SNIA). ... There are very few or no other articles that link to this one. ...

References

  1. ^ Stallings, William "Local Area Network Technology", Business Data Communications, 4th Edition, 2001 Prentice Hall, p. 370-371.

External links

  • Introduction to Storage Area Networks - Exhaustive Introduction into SAN, IBM Redbook

There are very few or no other articles that link to this one. ...

SAN Best Practices and Lessons Learned

  • InfoWorld Virtualization Report on Top 10 SAN Lessons

SAN Software Articles and White Papers

  • Whitepapers.Techrepublic.com Vendor white papers
  • Networkworld Storage Research Center
  • SearchStorage Storage Software Links
  • Virtual-Strategy Magazine Storage Virtualization White papers
  • Symantec Command central storage software
  • MPC Computers DataFRAME Series Modular SAN

  Results from FactBites:
 
What is storage area network? - a definition from Whatis.com - see also: SAN, storage network (409 words)
A storage area network is usually clustered in close proximity to other computing resources such as IBM z990 mainframes but may also extend to remote locations for backup and archival storage, using wide area network carrier technologies such as ATM or SONET.
Some SAN system integrators liken it to the common storage bus (flow of data) in a personal computer that is shared by different kinds of storage devices such as a hard disk or a CD-ROM player.
SANs support disk mirroring, backup and restore, archival and retrieval of archived data, data migration from one storage device to another, and the sharing of data among different servers in a network.
Managed Storage at Hosted Solutions - Storage Area Networks, Network Attached Storage, and Direct Attached Storage (417 words)
Network Attached Storage (NAS) was developed to allow the sharing of data files over an Ethernet network.
Storage Area Networks (SAN) were developed to allow organizations better disk utilization and performance.
By networking the storage, the drives that were once proprietary in usage, can now be placed in a central location and shared between multiple computers.
  More results at FactBites »

 
 

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