Storage area networks using the Internet Protocol and iSCSI technology could relieve the problems of networks being slowed down by data storage processes and e-business traffic.
Data storage has always presented difficulties for IT managers, and these difficulties are increasing with the growth of traffic across wide area networks (WANs) and Internet links. Firms are seeing local area network (LAN) traffic slowed by data storage processes, and e-business is suffering from slow data access. However, storage systems using Internet Protocol (IP) could relieve these problems.
Storage needs are doubling every year, according to research organisations. Individual direct-attached storage (DAS) limits for servers are being breached and firms are buying new servers purely to get more disk capacity. This is an expensive way of buying cheap disks, and causes management problems and data transfer bottlenecks.
The use of network-attached storage (NAS) devices is growing. NAS shares storage between servers by attaching a storage device or appliance to the network. This gets around the limitations of DAS by enabling disk farms to be created with special hardware and software such as Novell's NAS180, for example, which can scale up to 8TB. However, although stored data can be shared between servers and their clients, it still passes over the same IP LAN that clients and servers use to conduct e-business transactions.
'In all NAS the standard protocol is IP over an Ethernet infrastructure,' commented Bernard Zeutzius, Cisco's European storage networking prod- uct manager. 'The traffic slows down and NAS becomes a bottleneck itself. It's only suitable for low-end or departmental storage requirements.'
Another approach to these problems is to use a storage area network (SAN) a separate storage entity that interconnects servers and other storage devices via high-speed interfaces, such as Fibre Channel and a fast switch network fabric. SANs enable large volumes of storage traffic, such as online transactions or backup data, to be taken off the LAN while still providing file sharing capabilities, fault tolerance and scalability for growth.
While the SAN concept has been broadly applauded, its adoption so far has been limited. According to Zeutzius, this is because SANs are too complicated and not enough people are familiar with SAN technology. Another concern is the lack of standards and interoperability. Despite recent interoperability developments from hardware vendors Brocade, Compaq, EMC, Hitachi, IBM and McData, many IT managers are not convinced that different vendors' SAN equipment will work together, or with firms' storage management software.
Hardware manufacturers such as Cisco are now offering an alternative approach to Fibre Channel SANs IP storage. With IP storage, servers link to directly attached hard disks using the SCSI interface, and connect to SANs via Fibre Channel connections.
The standard being proposed for this purpose is the iSCSI protocol, which takes SCSI data packets from the servers and wraps them up in TCP/IP packets to be sent over Ethernet links to the SAN.
The SAN is front-ended by a router, which takes the iSCSI content and translates it into a format that the Fibre Channel SAN can handle. This effectively turns SANs into network-attached storage, while Gigabit Ethernet removes the LAN bandwidth limitations. As a result, SAN can talk to SAN, different servers can share SAN data, and the unifying effect of IP works its magic once again.
Cisco has produced its 5420 router to connect SANs to Gigabit Ethernet using iSCSI, and the standard also has the support of major hardware suppliers such as IBM, HP and Brocade. The Internet Engineering Task Force is also currently working on the protocol, so expect to see IP storage connecting to a LAN near you soon.