As a consequence, customers are sometimes sold solutions that do not fully address their problems, or they postpone making acquisitions despite the existence of viable but under-marketed solutions. Storage area networks, for example, offer many customer benefits, including reduced storage administration overhead and higher availability of data, but not all customers or departments within larger enterprises can realistically justify the investment in a SAN solution. As always, the key to matching a solution to a problem is a firm understanding of what the problem actually is.
SANs have made inroads primarily within the top tier enterprise networks. In these environments, the storage problems customers face are fairly obvious. The reactive and spontaneous acquisition of direct-attached storage and servers results in unwieldy and expensive storage administrative costs, under-utilized capacity, and bloated IT budgets that never quite catch up with growing data storage needs. Some large enterprises have thousands of servers and thousands of direct-attached storage arrays to manage, which not only requires a large staff of server and storage administrators, but frequently results in duplication of applications and files, and makes upgrading operating systems and applications untenable as well. Implementing SAN technology, on the other hand, provides a ready means for dramatically reducing the number of storage arrays and administrators, streamlining OS and application management, reducing the number of servers, and, as a side benefit, facilitating high availability of data via SAN-based data replication and server clustering.
Shared Storage for a Broader Market
For the productive application of SANs in medium and small businesses, the acquisition cost of a SAN solution must be significantly lower than that of conventional Fibre Channel SANs and not appreciably higher than the cost of direct-attached storage alternatives. This need is being addressed by storage platform providers in the form of lower cost modular shared storage arrays, more economical disk drives, and new IP-based storage products. In combination, these new technologies offer a lower entry cost for SANs and bring shared storage to a broader market.
Modular shared storage is designed to provide a lower threshold for implementing a storage network. Instead of buying a larger, more expensive chassis that can be filled with disks as needed, the customer can buy a compact chassis that can be integrated with other modular units over time. This pay as you grow option is bringing enterprise-class shared storage into the sub-hundred thousand dollar range while still providing many of the advanced RAID and high availability features common to higher end products.
The cost reduction offered by modular storage is augmented by lower priced disk drives with new serial-attached SCSI (SAS) or Serial ATA (SATA) interfaces. Disk drive technology for previously less reliable drives has improved significantly, making it feasible to commit mission-critical business data to commodity media. Although this technology maturation is cutting into the already thin margins of disk manufacturers, it is accelerating the development of high capacity, fast, reliable, and cheap storage solutions. Customers with relatively modest requirements and limited budgets can now consider the more economical shared storage options available in the market and circumvent the inevitable overhead that results from the continued accumulation of direct-attached storage.
More Affordable Shared Storage via iSCSI Although storage assets represent the lion's share of a SAN investment, cost reductions in server connectivity and the storage network infrastructure are also improving the total cost of ownership equation for SANs. iSCSI and IP storage switching are making shared storage more affordable by enabling customers to use more of their existing IP networks and staff to support storage applications. iSCSI is already available at no cost as a device driver that can be loaded on traditional, low cost Ethernet and Gigabit Ethernet network cards. Specialized iSCSI adapter cards with TCP off-load chips are currently available at less than half the cost of comparable Fibre Channel host bus adapters. Although iSCSI is currently unproven as a technology for higher end data center applications, it can sufficiently support normal storage applications such as block-based tape backup and moderate performance departmental data applications.
In addition to lower cost adapter cards, iSCSI offers further savings by leveraging conventional Ethernet and Gigabit Ethernet switches for the SAN core. Instead of tethering servers to dedicated and more expensive Fibre Channel fabric switches, servers can be deployed anywhere within an IP-routed network at less than half the cost per switch port. To benefit from this economy, however, the customer must understand their actual bandwidth and application requirements to avoid over-subscribing storage ports and degrading performance.
At the low end of the market, iSCSI-to-SCSI bridge products offer an affordable means to enjoy the benefits of shared storage at minimal cost. iSCSI-to-SCSI bridges enable customers to access their existing direct-attached SCSI storage devices from iSCSI-enabled servers. Some products in this class also provide rudimentary storage pooling capability as a means of simplifying storage allocation and administration. If the customer's SCSI devices are already in place, and if software iSCSI device drivers are used on the hosts, the entry point to a SAN is essentially free once the iSCSI-to-SCSI bridge is put in place.
iSCSI will not displace traditional Fibre Channel in the foreseeable future, but it does expand the market for SAN solutions in general. SAN storage arrays, for example, are still Fibre Channel-attached and require IP storage switches to provide protocol conversion between iSCSI and Fibre Channel. But since iSCSI dramatically reduces the cost of attaching additional servers, it facilitates bringing larger populations of devices into the SAN. Still, for high performance applications, Fibre Channel host bus adapters will remain the product of choice.
The combination of modular storage, more economical disk drives, and iSCSI host connectivity makes SAN solutions more economically attractive for departmental and small business applications. Customers who previously could not justify the expense of a SAN for their less critical applications can now gain the benefits of SAN technology on a more modest budget. As already demonstrated by Ethernet and IP technology, pervasive deployment and cost reduction create a mutually reinforcing cycle that benefits both customers and the industry.
Adapted from EnterpriseStorageForum.com