Internet Small Computer Systems Interface is a transport layer protocol that works on top of the Transport Control Protocol (TCP) and enables block-level SCSI data transport between the iSCSI initiator and the storage target over TCP/IP networks.
iSCSI stands for Internet Small Computer Systems Interface. iSCSI is a transport layer protocol that works on top of the Transport Control Protocol (TCP). It enables block-level SCSI data transport between the iSCSI initiator and the storage target over TCP/IP networks. iSCSI supports encrypting the network packets, and decrypts upon arrival at the target.
SCSI is a block-based set of commands that connects computing devices to networked storage, including spinning up storage media and data reads/writes.
The protocol uses initiators to send SCSI commands to storage device targets on remote servers. Storage targets may be SAN, NAS, tape, general-purpose servers – both SSD and HDD – LUNs, or others. The protocol allows admins to better utilize shared storage by allowing hosts to store data to remote networked storage, and virtualizes remote storage for applications that require direct attached storage.
The iSCSI protocol plays an important play in many different network configurations.
iSCSI Components
iSCSI Initiator, HBA, or iSOE
These technologies package SCSI commands into network packets and direct them to the storage target. The software-based iSCSI initiator is the least expensive of the options, and is often included in the operating system (OS).
Host-based adapters (HBA) is hardware device. HBAs are more expensive than software, but have higher performance with more functionality. A hardware alternative is to the full HBA is an iSOE card with an iSCSI offload engine. The engine offloads the initiator operations from the host processor, which frees up CPU cycles on the host servers.
iSCSI Target
iSCSI transports packets across TCP/IP networks. The iSCSI target is the remote storage, which appears to the host system as a local drive. The iSCSI protocol links the hosts and storage over IP networks: LAN, WAN, and Internet.
When the packets arrive at the iSCSI target, the protocol disassembles the packets to present SCSI commands to the operating system. If iSCSI has encrypted the network packet, it decrypts the packet at this stage.
iSCSI Performance
iSCSI performance is highly dependent on underlying technologies like 10 Gigabit Ethernet (10 GbE) and bridging technology in the data center.
* 10 GbE. Ethernet network connection speed has the single largest impact on iSCSI performance. Although smaller networks may run iSCSI protocols over 1 GbE networks, the slower speed is insufficient for mid-sized or enterprise data centers. Admins may increase some performance on a sub-10 GbE network by adding multiple NICs, but a single switch will not boost speed for multiple iSCSI ports. 10 GbE is the recommended speed for enterprise storage.
By Christine Taylor
