Any Kind, Anywhere Storage
iSCSI, the IP networking community?s answer to Fibre Channel for storage networking, will be an important protocol for IT managers to learn and implement when it is ratified next month. However, at least in the short term, eWeek Labs believes it won?t be a Fibre Channel killer.
In fact, IP over SCSI, which can link pools of storage across IP networks, will likely promote and expand the adoption of Fibre Channel as the dominant storage architecture. The first iSCSI devices are expected to be significantly slower than Fibre Channel products, which will limit iSCSI?s appeal in high-performance environments.
The iSCSI transport protocol allows SCSI commands to travel through IP networks, which in turn will allow IT managers to use high-speed IP networking technology such as routers, switches and Gigabit Ethernet to carry data from storage units (built of Fibre Channel hardware or SCSI hardware) to servers anywhere throughout a corporate network.
Network vendors including Cisco Systems Inc. claim that by moving storage networking tasks to iSCSI, IT managers can take better advantage of expensive investments they have already made in acquiring and implementing IP networking hardware. For example, they can share management tools and can implement security measures?such as virtual private networks and IP Security?across an IP network.
Another major benefit of using iSCSI is that the talent pool for knowledgeable IP networking staff is far greater than that for Fibre Channel storage networking experts.
It is important to note, however, that a commitment to iSCSI doesn?t necessarily mean that IT managers should be thinking about a full-scale convergence of storage and data networks. Until proper storage management and quality-of-service bandwidth management are developed for iSCSI, it would be best to keep these networks separate.
IP networking vendors will do a lot of work to optimize the buffer performance of iSCSI devices before the specification is finalized. And in a few years, iSCSI vendors will likely offer specialized processors to handle the networking and data encapsulation chores to boost performance.
In the meantime, it doesn?t make sense to rip out Fibre Channel installations.
The most important use for iSCSI technology will be for site-to-site mirroring of data. Although Fibre Channel is an excellent medium for clustering and data mirroring through campus networks, iSCSI can carry data across the country (provided the latency introduced by TCP/IP is acceptable to the applications run).
Unlike Fibre Channel, which is used primarily to link high-end and midrange servers to storage clusters, iSCSI can also be used to link network clients to shared SCSI and Fibre Channel devices, thus expanding storage area networks to the desktop and workstation realm.
In a Fibre Channel setup, when devices have to communicate through multiple connections, the Fibre Channel hardware knows the precise order of packets and drops them in order into memory. In the case of TCP/IP packets, when data comes into an adapter, it is copied into a TCP/IP buffer, where packets are sorted and eventually written into memory.
In storage circles, Fibre Channel?s favorable situation is known as ?zero copy? because data doesn?t have to be written into a buffer when moving between shared storage solutions to hosts.