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iSCSI provides the advantages of SAN storage while using an Ethernet networking infrastructure. iSCSI has tended to be deployed in small- and medium-sized businesses (SMBs) because of its lower initial costs and perceived simplicity, but it can scale up, especially with 10 GbE technology, and is increasingly finding a place in larger enterprises.
Because iSCSI runs over TCP/IP and Ethernet, it can run on existing Ethernet networks, although it’s recommended that iSCSI traffic be separated from regular LAN traffic. In theory, iSCSI can use any speed of Ethernet; however, the best practice is to use gigabit Ethernet or faster. Over the long-term, iSCSI will be able to use any of the speeds on the Ethernet roadmap, such as 40 Gbps and 100 Gbps.
Virtualized server environments can take advantage of iSCSI storage through the hypervisor or directly access iSCSI storage from the guest virtual machines (VMs), bypassing the hypervisor.
As the adoption rate of 10 GbE technology increases, iSCSI becomes increasingly attractive to organizations as they examine their long-term data center plans. Many of the iSCSI storage systems available today have all the advanced storage features such as replication, thin provisioning, compression, data deduplication and others that are often required by enterprise data centers. For many modern storage systems, iSCSI is available as a host interface along with FC and other interfaces.
Fibre Channel has been used as both a device-level disk drive interface and a SAN fabric interface, and has been deployed for approximately 15 years. FC carries the SCSI command protocol and uses either copper or fiber-optic cables with the appropriate connectors. FC speed has doubled approximately every three or four years, with 8 Gbps products becoming available in 2008 for SAN fabric connections and 16 Gbps products just beginning to emerge. All high-end storage subsystems and many midrange products use FC as either the only host interface or one of multiple interfaces.
Fibre Channel is used as a disk drive interface for enterprise-class disk drives, with a maximum interface speed of 4 Gbps to an individual disk drive (the speed of the interface shouldn’t be confused with the transfer rate of an individual disk drive). The industry is moving away from FC as an enterprise-class disk drive interface and shifting to 6 Gbps SAS for enterprise drives, including hard disk drives (HDDs) and solid-state drives (SSDs).
This was first published in October 2011