BANGALORE, INDIA: Internet Small Computer System Interface (iSCSI) failed miserably to live-up to the hype it generated back in 2003 and today, even after seven years, it is still considered a low-end technology.  

With issues, such as 'being the cheaper alternative to FCoE' (Fibre Channel over Ethernet), and 'SMB type', already been dealt with in earlier write-ups, let us here analyze a few others, which were and are still associated with  iSCSI.

Also Read: Time to get over the fibre fixation

Those issues, which prevented data center managers from taking up high-end networks over iSCSI networks, till sometime back.

Issue No 1: TCP/IP Overhead
There is a take that since iSCSI runs over TCP/IP (Transmission Control Protocol/Internet Protocol) it is susceptible to TCP "overhead".

K Raghavan, principal technical consultant, Cisco, says: “iSCSI runs directly on top of TCP/IP. Thus, there is CPU overhead in operating a TCP stack. For some applications with minimal I/O there is a minimal difference between iSCSI & native FC. However, for many there can be a huge CPU difference between the two.”

Hence, the performance of iSCSI has to deal with OS latency and CPU utilization on the iSCSI target rather than on the media, he added.

Harmeet S. Malhotra, enterprise solutions marketing director, Asia Pacific & Japan, Storage & Unified Fabric Solutions Marketing, Dell, explains that earlier, if a 1gigabit LAN card is used with iSCSI it eats away 1gigahertz of CPU performance. That means, if a server has 4giga hertz of total CPU capacity and I gigabit card is used,  it eats away 25 percent of the CPU performance.

However, not so anymore because today with  multi-core CPUs, one can achieve 20-40 gigahertz of server performance, he notes.

“Moreover, TCP/IP offload engine reduces the load of IGbps NIC from I gigahertz to a negligible amount, i.e 50 hertz, or 50,000 hertz, which is a mere .5 percent. So it probably has the same load on CPU as that of a fibre channel LAN card,” Malhotra adds.