Storage Area Network, SAN

In the simplest case, the SAN consists of DSS, switches and servers combined by optical communication channels. In addition to disk DSS directly, SAN can connect disk libraries, tape libraries (streamers), optical storage devices (CD/DVD, etc.), etc.

An example of a highly reliable infrastructure in which servers are connected simultaneously to a local area network (left) and to a SAN (right). This scheme provides access to data on the DSS when any processor module, switch, or access path fails.

With SAN, you can:

• Centralized management of server and storage resources
• Connect new disk arrays and servers without shutting down the entire storage system
• Using previously purchased hardware with new storage devices
• Online and reliable access to data drives far away from servers * without significant performance losses
• Faster Backup and Recovery - BURA

History

The development of network technologies has led to the emergence of two network solutions for DSS of systems - Storage Area Network (SAN) for block-level data exchange supported by client file systems, and servers for storage at the file level Network Attached Storage (NAS). To distinguish traditional storage from network DSS, another retronym was proposed - Direct Attached Storage (DAS).

The successive DAS, SAN, and NAS on the market reflect the evolving chains of communication between applications using data and the bytes on the media containing this data. Once the application programs themselves read and wrote blocks, then drivers appeared as part of the operating system. In modern DAS, SAN and NAS, the chain consists of three links: the first link is the creation of RAID arrays, the second is the processing of metadata that allows you to interpret binary data in the form of files and records, and the third is services for providing data to the application. They differ in where and how these links are implemented. In the case of DAS, the DSS be "bare"" it only provides the ability to store and access data, and everything else is done on the server side, starting with interfaces and a driver. With the advent of SAN, RAID is transferred to the DSS side, everything else remains the same as in the case of DAS. And NAS differs in that metadata is also transferred to the DSS to provide file access, here the client can only support data services.

SAN became possible after Fibre Channel (FC) was developed in 1988 and ANSI was approved as a standard in 1994. The term Storage Area Network dates from 1999. Over time, FC gave way to Ethernet, and iSCSI-connected IP-SANs became widespread.

The idea of ​ ​ a NAS network storage server belongs to Brian Randell from the University of Newkastle and was implemented in machines on a UNIX server in 1983. This idea was so successful that it was picked up by many companies, including Novell, IBM, and Sun, but ultimately replaced the leaders of NetApp and EMC.

In 1995, Garth Gibson developed the principles of NAS and created Object Storage (OBS) DSS. He began by dividing all disk operations into two groups, one including more frequently performed ones, such as reading and writing, and another rarer one, such as name operations. Then he offered in addition to blocks and files another container, he called it an object.

OBS is distinguished by a new type of interface, it is called object. Client data services interact with metadata over an object API API. OBS not only stores data, but also supports RAID, stores metadata related to objects, and supports an object interface. DAS, SAN, NAS, and OBS coexist in time, but each of the access types more closely corresponds to a specific type of data and applications.

Read more about DSS evolution here.

SAN Architecture

Network Topology

The SAN is a high-speed data network for connecting servers to storage devices. A variety of SAN topologies (point-to-point, Arbitrated Loop, and switching) replace traditional server-to-storage bus connections and provide greater flexibility, performance, and reliability in comparison. The SAN concept is based on the ability to connect any of the servers to any storage device running over Fibre Channel. The principle of interaction of nodes in a SAN with point-to-point topologies or switching is shown in the figures. In SANs with an Arbitrated Loop topology, data is transferred sequentially from node to node. In order to start data transmission, the transmitting device initializes arbitration for the right to use the data transmission environment (hence the name of the topology - Arbitrated Loop).

Arbitration logic loop

Switching

Point-to-point

The transport basis of the SAN is the Fibre Channel protocol, which uses both copper and fiber connections of devices.

SAN Components

SAN components are divided into the following:

• Host Bus Adaptors (HBA);
• Storage resources;
• Devices that implement the SAN infrastructure;
• Software.

Host Bus Adaptors

HBAs are installed on servers and communicate with SANs via Fibre Channel. The Fibre Channel protocol stack is implemented within the HBA. The most famous HBA manufacturers are Emulex, JNI, Qlogic and Agilent.

Storage resources

Resources data storage include, and disk arrays tape drives libraries with an interface. Fibre Channel Many of their storage capabilities are implemented only when they are included in the SAN. Thus, high-end disk arrays can carry replication data between arrays over Fibre Channel networks, and tape libraries can implement data transfer to tape directly from disk arrays with a Fibre Channel interface, bypassing the network and (). servers Serverless backup Disk arrays of companies,,, (EMC Hitachi IBM the family Compaq inherited Storage Works from) have gained the greatest popularity in the market, and of Compaq Digital the manufacturers of tape libraries should be mentioned,,. StorageTek Quantum/ATL IBM

SAN Infrastructure Appliances

The devices that implement the SAN infrastructure are switchboards Fibre Channel (, Fibre Channel switches FC switches), (concentrators Fibre Channel Hub) and (routers Fibre Channel SCSI routers). Concentrators are used to combine devices operating in Fibre Channel Regulated Loop () mode FC AL. Using hubs allows you to connect and disconnect devices in a loop without stopping the system, since the hub automatically closes the loop if the device is disconnected and automatically opens the loop if a new device has been connected to it. Each change in the loop is accompanied by a complex process of it. initialization The initialization process is multi-stage, and it is not possible to exchange data in a loop before it ends.

All modern SANs are built on switches that allow you to implement a full-fledged network connection. Switches can not only connect Fibre Channel devices, but also distinguish access between devices, for which the so-called zones are created on the switches. Devices placed in different zones cannot communicate with each other. The number of ports in the SAN can be increased by connecting switches to each other. The group of connected switches is called Fibre Channel Fabric or simply Fabric. Communication between switches is called Interswitch Links or ISL for short.

Software

The software allows you to implement backup of server access paths to disk arrays and dynamic load distribution between paths. For most disk arrays, there is a simple way to determine that ports accessible through different controllers belong to the same disk. Specialized software supports a table of device access paths and provides path disconnection in the event of an accident, dynamic connection of new paths and load distribution between them. Typically, disk array manufacturers offer specialized software of this type for their arrays. VERITAS Software manufactures VERITAS Volume Manager software designed to organize logical LUNs from physical disks, providing disk path redundancy and load balancing for most known disk arrays.

Protocols used

Storage networks use low-level protocols:

• Fibre Channel Protocol (FCP), SCSI transport over Fibre Channel. The most commonly used protocol. It exists in variants 1 Gbit/s, 2 Gbit/s, 4 Gbit/s, 8 Gbit/s and 10 Gbit/s.
• iSCSI, SCSI transport over TCP/IP.
• FCoE, FCP/SCSI transport over clean Ethernet.
• FCIP and iFCP, FCP/SCSI encapsulation and transmission in IP packets.
• HyperSCSI, SCSI transport over Ethernet.
• FICON transport via Fibre Channel (used only by mainframes).
• ATA over Ethernet, ATA transport over Ethernet.
• SCSI and/or TCP/IP transport via InfiniBand (IB).

Advantages

• High reliability of access to data on external storage systems. Independence of SAN topology from used DSS and servers.
• Centralized data storage (reliability, security).
• Convenient centralized management of switching and data.
• Transfer heavy I/O traffic to a separate network - LAN offload.
• High speed and low latency.
• Scalability and flexibility of logical SAN structure
• The geographic size of the SAN, unlike classic DAS, is practically unlimited.
• The ability to quickly allocate resources between servers.
• The ability to build failover clustered solutions at no additional cost to your existing SAN.
• A simple backup scheme - all data is in one place.
• Availability of additional features and services (snapshots, remote replication).
• High SAN security.

Sharing storage typically simplifies administration and adds a fair amount of flexibility because cables and disk arrays do not need to be physically transported and remounted from one server to another.

Another acceptability is the ability to download servers directly from the SAN. With this configuration, you can quickly and easily replace the failed one by server reconfiguring the SAN so that server the replacement will boot from the LUN failed server. This procedure can take, for example, half an hour. The idea is relatively new, but already used in the latest. data-centers

SANs also help you recover more efficiently after a failure. A SAN can include a remote site with a secondary storage device. In this case, you can use replication - implemented at the level of array controllers, or using special hardware devices. Because IP-based WANs are common, Fibre Channel over IP (FCIP) and iSCSI protocols have been developed to extend a single SAN through IP-based networking . Demand for such solutions increased significantly after the events of September 11, 2001 in the United States.

Shortcomings

All disadvantages are reduced only to the high cost of such solutions. The Russian DSS market as a whole lags behind the market of Western developed countries, especially in the widespread use of storage networks. In particular, the shortage and high cost of high-speed communication channels continue to have a certain impact.

Difference from NAS

The main difference between SAN and NAS is the way storage devices communicate with servers. Generally speaking, the SAN architecture aims to solve problems caused by intensive backup and communication procedures by moving the entire system to a dedicated subnet. Fibre Channel-based SANs allow you to widely modify storage capacity and guarantee higher throughput within a dedicated subnet (Disk arrays and Tape Libraries that are not equipped with Fibre Channel interfaces can be connected to a SAN using Fibre Channel-SCSI routers).

Market estimates

2024: Global Storage Area Network Market Size Reaches $21.96

At the end of 2024, costs in the global storage area network (SAN) market amounted to $21.96 billion. The North American region accounted for almost 40% of global spending. Industry trends are addressed in the Precedence Research study, which TAdviser reviewed in mid-September 2025.

The SAN architecture involves the creation of a separate storage network that combines with the server hardware. It is a high-speed infrastructure that provides access to consolidated data stores. For SAN implementation, special technologies have been developed in the field of software and hardware, as well as network interaction. With SAN, storage devices on multiple heterogeneous platforms can be combined into a single, centrally managed system. The advantages of this approach are:

• Scalability - SAN supports very large deployments;
• High performance - SAN uses a separate network structure for storage-related operations;
• Simplified management - From a SAN perspective, it is a single entity;
• Physical remoteness of data - making it much easier to create copies in case of natural disasters or man-made accidents;
• High availability.

One of the drivers of the analytics market is the active digital transformation of enterprises in various fields. This process is accompanied by the migration of business loads to hybrid and multi-cloud environments, which necessitates the creation of SAN systems that provide high-speed connection and reliability. The rapid growth of virtualized environments and today's data centers increases the need for centralized, high-availability storage networks. In addition, the active use of artificial intelligence, machine learning and real-time analytics requires the implementation of reliable storage solutions, which contributes to increased demand for SAN solutions.

Another simulation is the need for business continuity. Companies are prioritizing information resilience and disaster recovery as cyber attacks and system failures increase. SAN platforms offer advanced backup and replication features that guarantee security and fast recovery.

However, the significant capital costs required to build a SAN infrastructure, including network software and hardware components, may be too high for small and medium-sized enterprises, hampering market expansion. SAN also requires the involvement of highly qualified IT staff.

The lion's share of revenue in the SAN segment comes from hardware. Geographically, North America leads, accounting for 38% of revenue in 2024. Europe is in second place with 29%, and the Asia-Pacific region closes the top three with 22%. This is followed by Latin America with 8%, followed by the Middle East and Africa with 3%. The major players on a global scale are:

• Dell Technologies;
• HPE;
• IBM;
• Cisco Systems;
• Broadcom;
• NetApp;
• Hitachi Vantara;
• Fujitsu;
• Huawei Technologies;
• Lenovo Group;
• Pure Storage;
• DataCore Software;
• StarWind Software;
• Nutanix;
• NEC.

Precedence Research analysts believe that in the future, the CAGR in the SAN market will be 5.25%. Thus, by 2034, costs may increase to $36.63 billion.^[1]

See also

• Software-Defined Storage (SDS)
• Direct Attached Storage, DAS
• Network Attached Storage (NAS)
• DSS Product and Project Catalog
• Data backup

• Andrey Zakharov, Key Storage Systems and Features
• SANs

Notes