Simplifying storage: combining the iSCSI standard with SAN functionality

Computer Technology Review, May, 2004 by Tom Major

As networked storage becomes more prevalent, the intelligent services required to effectively assign, secure, and manage these network resources become all the more critical. Layer 2 and Layer 3 services such as virtual LANs (VLANs), quality of service (QoS), high availability, routing, management, and access control lists (ACLs) are key services that IP and Ethernet technologies are able to provide to a storage networking infrastructure today that Fibre Channel does not.

* Greater access to necessary technical skills: IT workers with Ethernet and IP skills are far more abundant and affordable than Fibre Channel specialists.

* Lower total solution costs: In addition to storage prices that are typically considerably lower than Fibre Channel storage, there's no investment in expensive Fibre Channel HBAs and switches, and no investment in acquiring Fibre Channel expertise. Ethernet costs are known and predictable as with any mature technology.

* Lower cost of ownership: Instead of developing storage networks with unfamiliar storage connection technologies, network managers can use the IP/Ethernet skills of existing staff, shortening the time and expense to deliver complete solutions. While it is typically suggested that users deploy a dedicated network (the IP SAN) for shared storage, the deployment of gigabit Ethernet enables network managers to benefit from immediate interoperability, network management, best practices, and analysis tools.

Many sites also need to establish backups and disaster recovery support for critical data, frequently at remote facilities. Because Fibre Channel is limited to 10km, conversion to the IP protocol is necessary for replication over a long distance. This introduces significant cost to the Fibre Channel infrastructure. Utilizing iSCSI in an IP SAN allows users to move data over long distances much more affordably, without any protocol conversion.

These benefits of a standard will encourage the development of more iSCSI-based storage devices and the construction of more IP SANs. In fact, the IT industry is ripe with the buzz of iSCSI or IP SANs. Realistically, however, iSCSI is no more than a protocol, enabling block-based connectivity to a server over a standards-based network. Connectivity alone does not lower costs or increase management efficiency.

The Benefits of a SAN

To realize the potential of IP SANs--cost savings combined with full network storage functionality--users need to realize the benefits now available with Fibre Channel SANs:

Dynamic Scalability

The consistent growth of data and the demand that applications be available around the clock mandates that storage scale without downtime. However, dynamic scalability is only a partial fix. Ideally, a networked storage solution automates the process of re-allocating disk usage across the network as capacity is added. With both DAS and NAS solutions, all data movement associated with adding additional captive storage or a new NAS box requires the administrator to manually move and balance data amongst the servers. This is a very labor-intensive process. Some IP SAN solutions automate this capability.