Companies producing storage subsystems for three years now repeat directly connected storage systems (DAS) is not enough flexibility, they create bottlenecks, and at the same time, the time required to administer them fairly large. The future of networked storage systems, which will have a repository anywhere on your network. And iSCSI technology is precisely designed to move storage to a new level. But if iSCSI is so beneficial, why we do not see widespread use? The fact is that except for very expensive infrastructure Fibre Channel, which is required for high-speed solutions, there is also a technical barrier. To understand the reasons for such slow spread of iSCSI, should consider in detail the protocol itself and its evolution.
The iSCSI protocol provides for the encapsulation of data in the IP-packets, which allows transmitting information on existing networks in the same way as in the case of an ordinary locally-attached storage device, such as UltraSCSI. Because of the wide variety of networks, IP (PAN, WLAN, LAN via Ethernet or Fibre Channel, WAN, MAN and LAN), storage area network (storage area network, SAN) based on the iSCSI protocol can easily overcome any distance because it is limited only performance networks used.
With this in mind it is understandable that the SAN is usually not extending beyond the limits of fast networks, which gives the mentioned technical barriers. Memory serving many customers should have the necessary bandwidth for this. Ethernet network at 100 Mbps, for example, could easily cope with iSCSI technically, but her performance is too little. Fibre Channel, by contrast, is too expensive technology for small and medium businesses.
The rapid development of Gigabit Ethernet, in fact, creates the foundation for applications iSCSI. While the most powerful and advanced gigabit network using optical, Gigabit Ethernet over copper will accelerate the transition from direct attached storage to network storage. This infrastructure is backward compatible, and pleasantly pleased its price. iSCSI stands for Internet SCSI, with SCSI, in turn, stands for Small Computer System Interface "(small computer system interface), towering over the other storage interfaces DAS in the professional field.
Connectivity:
The concept of iSCSI has arisen due to the fact that the interfaces such as ATA or SCSI limited to one computer and a maximum length of cable. So the flexibility of business applications, as well as corporate-level tasks is very limited. Ideally, the storage subsystem is better to withdraw from specific servers, to increase flexibility and to avoid bottlenecks. As a result, administrators can add, move, backup, restore and reconfigure the storage system without reference to any servers. And the use of existing network infrastructure for such stores - even a very good idea.
Of course, you can spend several hundred dollars on a SCSI cable or, worse, a lot of money on cables and accessories Fibre Channel. Today, Fibre Channel has become the main interface for professional applications and SAN because of the high bandwidth and large working distance. Indeed, the Fibre Channel connection can extend up to 30 meters in length using twisted copper pairs or up to 10 km during the transition to fiber-optic cable and transmission rate can be 2 Gbps or 4 Gbps. So the Fibre Channel network is quite capable to connect several buildings, while ensuring a very high speed and performance.
In addition, Fibre Channel can connect two devices on a point-point, used in conjunction with switches or work in controlled topologies resembling Token Ring. Finally, the technology is successfully coping with cells (cell) ATM, IP packet or SCSI, using their own frames (they are not compatible with Ethernet). For these reasons, Fibre Channel, and is dominated by the corporate sector.
But the components of Fibre Channel makes sense to buy only high-end environments: data or large databases. Infrastructure can be used as an interface between the hard drives and controllers, or to connect systems and storage units within the SAN (or both at once). However, if your corporate environment does not require extreme speeds, the additional spending meaningless. Why not, then select the Hardware Serial ATA, as well as the infrastructure is not dwell on the Gigabit Ethernet.
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