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What is ethernet switch?
Mar 14, 2017

Fiber Switch is a high-speed network transmission relay equipment, it is more common than the use of fiber optic cable as a transmission medium. The advantages of optical fiber transmission is fast, anti-interference ability.


In the previous data storage are basically in the server directly connected to several SCSI, IDE and the like disk, which is what we often hear the DAS (direct connection storage) way. This point-to-point disk system is clearly difficult to expand and storage performance is difficult to improve the lack of. Not only that, by the IDE and SCSI interface physical performance constraints, and its connection to the disk is usually only up to 20 meters within the connection distance, greatly limiting the disk storage system expansion.

In order to solve these deficiencies in the above DAS storage methods, network equipment manufacturers and standards experts began to consider the development of a new storage technology, a fundamental solution to DAS storage mode transmission rate and connection distance. At first people think of a storage system is independent, as a network device on the network node, which can greatly reduce the server's data storage load, but also can greatly expand the disk storage system, which is the later NAS (network Additional storage) mode.

This storage is indeed a considerable extent to solve the previous DAS storage deficiencies, to meet the vast majority of small and medium enterprises for local storage needs. And it is the biggest feature is simple, with the same IP protocol with the Ethernet, network administrators can easily grasp the deployment of NAS storage system, by many enterprises are widely welcomed. But NAS is still not fundamentally solve the disk storage performance and connection distance problem, in general, disk storage performance has not been fundamentally improved, but to improve the network export bandwidth.

It is because the NAS is still the above shortcomings, so people continue to develop a new way of network storage, that is, SAN storage. The biggest feature of this storage is the Fiber Channel (Fiber Channel) protocol that provides Gigabit serial network access for storage devices, and then builds Fiber Channel-based on Fiber Channel's fourth layer, The SCSI protocol used for storage, the IP protocol for the network, and the virtual interface (VI) protocol mapped to the network architecture, so that various network types of network devices and channels can be supported. The Fiber Channel protocol combines a number of advantages, such as a network range of up to 10 kilometers, a simple serial cable that can use multiple media, a gigabit network rate, and a variety of protocols that can be used simultaneously on the same cable.

A SAN is a network of storage devices and system components. All communications are done on a Fiber Channel network and can be used to centralize and share storage resources instead of NAS storage as a network node Of the network equipment. SAN not only provides high-performance connectivity to data devices, improves data backup speed, and adds redundant connectivity to storage systems, providing support for highly available cluster systems. Simply put, SAN is a dedicated Fiber Channel network (different from Ethernet) that connects storage devices and servers, but it has a similar architecture to Ethernet, as well as servers that support Fiber Channel, Fiber Channel cards (Fiber Channel), Fiber Channel Hub / switch and Fiber Channel storage devices. Technically speaking, the three most important components of SAN networks are: device interfaces (such as SCSI, Fiber Channel, ESCON, etc.), connecting devices (switches, gateways, routers, hubs, etc.) and communication control protocols such as IP and SCSI Wait). These three components, together with additional storage devices and servers, form a SAN system.

With the increasing number of enterprise network data and frequent network applications, many companies are beginning to realize the need to specifically build their own storage system network to meet the ever-increasing data storage performance requirements. At present, the most popular data storage network is SAN (Storage Area Network, storage area network), is the entire storage as a separate network and server where the enterprise LAN connection.


It is characterized by the use of high transmission rate of fiber channel and server network, or SAN network internal components of the connection, so that the entire storage network has a very wide bandwidth for high-performance data storage provides a guarantee. In this SAN storage network, the key role is that we often hear the fiber switch (FC Switch, also known as "Fiber Channel switch" and "SAN switch"). Because this is a new type of equipment, and we usually see, the use of Ethernet switches have too many differences (mainly in the agreement on the support), so many readers, or even have used SAN storage network Of the enterprise users are little knowledge of the SAN switch. To this end, this article on the SAN switch to buy when you need to pay attention to the matters to introduce you, in fact, is about the main features of the SAN switch. Let's take a brief look at the origin of the SAN switch, which will allow us to deepen our understanding of the SAN switch and no longer be "mysterious".


The fiber-optic Ethernet switch is a high-performance managed Layer 2 fiber-optic Ethernet access switch. Users can choose all-optical port configuration or optical port hybrid configuration, access to fiber-optic media optional single-mode fiber or multi-mode fiber. The switch can support network remote management and local management to achieve the port working status of the monitoring and switch settings.

Fiber ports are particularly suitable for information points Access distance beyond the five categories of access distance, the need for anti-electromagnetic interference and the need for confidential communications and other occasions applicable areas include: residential FTTH broadband access network; enterprise high-speed fiber LAN; high reliability industrial distribution Control system (DCS); optical fiber digital video surveillance network; hospital high-speed optical fiber local area network; campus network.


Because the switch is the core component of the SAN that constructs the storage area network, it is critical to choose the most appropriate switch. Only the right choice for the storage area network the most suitable fiber switch to improve the efficiency of enterprise information management to meet the most challenging needs. From the previous introduction can clearly see that the SAN network and the traditional Ethernet is essentially different, but the network equipment manufacturers for the different understanding of the SAN, so there have been a variety of equipment interface and channel protocol SAN system. This is the previously described SCSI, Fiber Channel, ESCON, FICON, etc., channel protocol also has Fiber Channel (FC) protocol, SCSI and FCIP protocol several. These different interfaces and channel types determine the overall SAN network system deployment in the choice of equipment is still relatively complex. Here we introduce a few major considerations.

Channel protocol support

There are several different types of channel protocols used by SAN switches, such as the FC, SCSI, and FCIP protocols described earlier. Different support supports different types of device interfaces. FC protocols are generally supported by all SAN switches, and SCSI protocols may be supported in middle and low fiber switches. The FCIP protocol based on the Ethernet IP protocol now also has support for many vendors' SAN switches because of its relatively simple cost, Very popular with business users.

Number of ports

SAN switches and the usual access to the Ethernet switch has a significant difference is that the number of ports is very large, very high degree of intensity. The total number of SAN switch ports are more than 48, the highest has reached 256, of course, low-end entry-level SAN switches also have 16 or less. The SAN switch needs so many ports, because it is connected with the Ethernet switch is different, of course, mainly reflected in the multi-SAN switch network. In a SAN network, each SAN switch must be connected to other SAN switches (as shown in the following figure). This one-way connection makes it obvious that the exchange rate of data can be greatly increased. Because some of the switches in the switch is used for the connection between SAN switches, so the actual available SAN switch port is less, for a small number of ports on the SAN switch is clearly not suitable, so the SAN switch ports are generally more , At least 24 or more. 

Whether to support stacking

Workgroups and above of the SAN fiber switches also support stacking, through stacking to reach the purpose of extending the switch ports and overall backplane bandwidth. SAN switches can be stacked through E_Ports (extended ports), which can extend the fiber network to thousands of nodes, and the current technology can stack up to 239.

Extensible performance

Any storage area network will not be static, it is always faced with expansion and new technology, new product integration issues. The storage area network is through flexible scalability to meet future needs, thus protecting the user's investment. Its scalability also includes two aspects, on the one hand is the expansion of the size of the storage network, the original system can not meet the user's storage needs how to expand into a larger fiber storage network; the other hand, Technology development, can successfully upgrade to new technologies and applications. For example, the development of IP storage makes it more important for users to consider iSCSI and FCIP, FC switches in the future can be extended IP storage is very important.

Redundant performance

If you want to ensure the continuous operation of critical business, you need to build the system in a redundant way. Redundancy scheme In fact, the server type, the program is a variety of, can be a single switch parts redundancy, you can also consider the use of dual-fiber switching network redundancy configuration program, but this cost is very high. But because of this dual-network topology to ensure redundancy, so you can use a cheaper single-power switching device can be, even if a switch failure, the host and the storage array link switching software will automatically switch to switch Remedy on the device until the faulty device is replaced. If the regular downtime maintenance does not affect the application of the enterprise, then use a hot-swappable redundant power supply and fan switches can be greatly reduced costs. While also ensuring that any single point of failure of the power supply or fan does not affect the operation of the network.

In short, there are a number of areas to consider before choosing which switches to use to build a SAN fabric switching network. As with other device sourcing plans, you need to prioritize future key requirements before comparing switches, as well as prioritize these requirements.

In fact, fiber switch technology is very complicated, the type of protocol and interface is also increasing, increasing performance, there are many aspects to note, but limited to space reasons In this article can only play a role for everyone, hoping to you in the purchase of fiber switches have a certain reference value.