iSCSI

What is iSCSI Storage?

 

The iSCSI refers to Internet Small Computer System Interface, is a protocol for storage area networks that specifically defines how data is transferred between hosts and storage devices. It enables block-level SCSI data transfers between an iSCSI initiator and a storage target over a TCP/IP network. iSCSI storage, also known as iSCSI SAN (Storage Area Network) storage, is a cost-effective alternative to traditional Fibre Channel (FC) SANs. Unlike FC SANs, which require specialized hardware (such as FC host bus adapters and FC switches), iSCSI SAN storage can be built using existing network infrastructure (such as Ethernet switches and routers), with no need to purchase additional equipment at all. In addition, iSCSI is based on the block transfer standard, which is fast and efficient.

 

How Does iSCSI Storage Work?

 

To better understand how iSCSI works, it is important to first know some key components, such as the iSCSI initiator and the iSCSI target. iSCSI initiator is software or hardware installed on the server that sends requests to and receives responses from the iSCSI target. The iSCSI target, on the other hand, is located on the storage device and is responsible for listening to and processing commands from the initiator. The initiator is typically located on the client computer and is commonly software-initiated.

 

Simply put, iSCSI storage transfers block-level data over a TCP/IP network connecting the iSCSI initiator on the server to the iSCSI target on the storage device. iSCSI protocol encapsulates SCSI commands into packets at the TCP/IP layer, which are then transmitted over the network via a point-to-point connection. When the packets arrive, the iSCSI protocol disassembles them and extracts the SCSI commands so that the operating system can treat the storage as a locally attached SCSI device and format it as usual.

 

Advantages of iSCSI

 

There are quite a few advantages to iSCSI for enterprises that use it as part of their SAN infrastructure. Here are a few of the most notable ones:

 

TOE Integration: Many network interface cards (NICs) are equipped with a built-in TCP offload engine (TOE), which shifts TCP/IP processing tasks to the network controller, taking pressure off the host CPU.

 

Affordable Initial Setup: Using the iSCSI protocol, enterprises can maintain a low total cost of ownership (TCO) when accessing storage devices. Therefore, the SAN that is built is not only cheap, but also simple to install and maintain.

 

No Additional Hardware Required: Since iSCSI is based on IP technology and leverages the interoperability of TCP/IP and Ethernet, there is no need to purchase additional hardware.

Enhanced Security: iSCSI provides an additional layer of security to the storage network for enhanced data protection.

 

Minimal Training and Maintenance Costs: iSCSI does not require too much training for network personnel and is easy to use, which increases storage utilization while reducing operational costs.

 

Wide compatibility: As a universal, non-proprietary technology, iSCSI can work with common network storage devices seamlessly and has excellent compatibility.

 

Scalable Flexibility: iSCSI SAN environments can be easily scaled using existing network hardware, enabling organizations to increase storage capacity on demand.

 

Reduced power consumption and costs: By reducing the number of active switches and simplifying the infrastructure, iSCSI helps reduce power consumption, cooling costs and overall infrastructure costs.

 

Limitations of iSCSI

 

The next part is the induction of limitations of iSCSI, you also need to be concerned about these points before implementing:

 

Performance dependency: If both business data and iSCSI traffic are processed on the same network, it may lead to increased latency and performance degradation.

 

Incompatibility with SSDs: iSCSI is not well suited for solid-state storage devices (SSDs) due to its reliance on serial technology.

 

Capacity Limitations: Hard drive LUNs are limited to a maximum capacity of 250TB and NAS is limited to a maximum capacity of 144TB.

 

Limited number of snapshots: iSCSI applications support up to 512 snapshots (virtual copies of data), while file-shared volumes support only 64 snapshots. Failure of the snapshot function may result in data loss and impact iSCSI performance.

Connection limitation: iSCSI sessions can have a maximum of 255 connections, once this number is exceeded, the target will reject other connection attempts.