What is iSCSI in the Computer Network?

iSCSI represents Internet Small Computer Systems Interface. It 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.

There are multiple means of transports that can be used for iSCSI. The most common is TCP/IP over Ethernet, but Remote Direct Memory Access (RDMA) can also be used with iSER, which is iSCSI Extensions for RDMA. If using iSER, the transport is RoCE or InfiniBand, and the underlying network is Ethernet (for RoCE) or InfiniBand (for InfiniBand transport).

Components of iSCSI

There are two major components of iSCSI, which are as follows −

Initiator

These initiators set the commands into the network packets and instruct them to transfer at the iSCSI target. A software-based initiator is used at the operating system to perform this data packet transport. There are also hardware devices such as HBA (Host Bus Adapters) with high-level encryption functionality.

Target

iSCSI target is the storage device that appears as a local drive to the host system. When data packets arrive at the target, the set of commands are implemented to disassemble them in the operating system and access the underlying storage.

How iSCSI Works

iSCSI encapsulates SCSI commands and data into TCP/IP packets for transmission over standard Ethernet networks. The initiator sends SCSI commands over the network, and the target processes these commands and returns responses. This allows remote storage to appear as locally attached disks to the operating system.

Features

There are various features of iSCSI, which are as follows −

• IP Routing − One of the important features of iSCSI is that it uses TCP/IP Protocol. TCP/IP enables long-distance IP routing without the requirement for external gateway hardware. It also supports high flexibility and a large storage network environment.

• Security − It is used for securing IP traffic in the network by authenticating and encrypting each data packet received in the network through IPSec and CHAP authentication.

• Storage Array − iSCSI targets can be implemented in large storage arrays. The arrays can be free software-based or commercial products. They usually provide unique iSCSI targets for multiple clients or users.

• Standard Ethernet − It uses Standard Ethernet infrastructure, and because of this, it does not require expensive specialized components like Fibre Channel, making it cost-effective.

Advantages and Disadvantages

Conclusion

iSCSI provides a cost-effective method to implement block-level storage over standard TCP/IP networks, enabling organizations to leverage existing Ethernet infrastructure for storage area networks. It offers flexibility and security features while maintaining compatibility with SCSI storage protocols.