By Heidi Biggar
Some consultants and vendors believe backup will be the first real "killer app" for iSCSI storage area networks (SANs), just as it was for Fibre Channel SANs. Advanced Digital Information Corp. (ADIC) is one of those vendors.
Last month, ADIC announced iSCSI options for two of its low-end and midrange tape offerings: the Scalar 24 and Scalar 100, respectively. In doing so, the company became the second tape vendor to offer native iSCSI support. About a year ago, Spectra Logic announced iSCSI support for its Spectra 64K, 20K, and 2K tape libraries and NAStape stand-alone tape drives.
Other iSCSI components, including host cards, disk subsystems, switches, routers, and backup software, are available from a variety of vendors (see "Influx of iSCSI products continues," above).
ADIC officials believe that—at least in the case of backup—the lack of iSCSI tape targets was in part responsible for low adoption of iSCSI last year.
Despite forecasts to the contrary, user adoption of iSCSI SANs did not materialize in 2003. Still, analysts expect users to implement the technology on a significantly greater scale this year, citing once again the benefits of low-cost storage networking, the simplicity and ubiquity of Ethernet networking (versus Fibre Channel), and the ability to transmit I/O commands over distance for backup and disaster-recovery purposes.
ADIC says it is taking a cautious approach to iSCSI, first targeting small to medium-sized companies that can benefit from backing up to native iSCSI tape libraries over LANs or in IP SAN environments.
"iSCSI is ideal for a certain class of backup users," says Steve Whitner, director of marketing at ADIC.
"There is a lot of pent-up demand for both a real low-cost entry and for an IP SAN-type entry," he adds.
Whitner says that iSCSI provides an easy path for network backup and consolidation that is much better than direct-attached backup, which is limited by management overhead, scalability issues, tape utilization issues, and data vulnerability.
While server-based LAN backup addresses some of the issues with data vulnerability and media usage, this type of architecture can still be plagued with processor consumption, networking congestion, and performance and scalability issues—all of which can create backup window pressure, according to Whitner.
ADIC recommends attaching iSCSI tape systems directly to the LAN, creating a virtual LAN (vLAN), or to a separate IP SAN network (see diagrams). This allows users to consolidate the backup process with few limitations.
Of the two approaches, the first is the simpler and cheaper option because it plugs directly into the network and leverages existing network infrastructure (e.g., switches and network interface cards). On the downside, because network and storage traffic both travel over the LAN, they share bandwidth, which could present problems depending on the backup window.
In an IP SAN environment, network and storage traffic are separate, which means fewer data-contention issues and improved performance. Other benefits of this type of configuration include per-server choice of NICs and/or HBAs and physical security between network and storage traffic. However, this approach requires an additional switch, which drives up total costs.
ADIC expects to begin shipping its iSCSI library option this month.