The Business Case for Storage Networks [Electronic resources] نسخه متنی

The Move to Storage Networks

A number of business drivers precipitated the move to storage networks at the CTRC. Distance is the primary issue that drove the need for a networked solution to the storage management problem, as previously discussed; however, other solutions on the market could have solved the replication problem facing the CTRC, although with a significant increase in management and capital costs.

Initial Fibre Channel deployments were successful (Luter has utilized both Brocade and Cisco Fibre Channel switches to increase storage utilization), but without the use of the IP backbone to transport data across the MAN to the secondary datacenter, or without the purchase of an expensive SAN extension product, it was not possible to keep the data synchronized between both locations.

The financial and business justification for an IP-based storage network became clear after Luter and the management team at the CTRC analyzed the investment protection offered by an iSCSI solution. Considering the significant investment already made in an IP infrastructure for VoIP and WAN and LAN networking, and the capability to boost the utilization of the backbone infrastructure to avoid the costs associated with building a separate Fibre Channel network for extending the SAN, the rationale behind selecting iSCSI as a technology enabler is clear.

In addition to the bottom-line impact of implementing iSCSI, the use of network boot functionality over iSCSI provides ease of management for the 45 hosts on the network, all of which can boot from multiple boot images (for flexibility) and multiple boot paths (for redundancy) across the SAN. In terms of economies of scale, network boot via iSCSI allows the administrators in either location to apply patches and upgrades to the host operating system only once, instead of multiple times. In addition, having multiple copies of boot images available across the IP network offers an increased level of redundancy and flexibility for host management purposes.

Luter and his team clearly qualify as early adopters of iSCSI technology in the enterprise datacenter. The first implementation of iSCSI at the CTRC was built around the Cisco SN5420 storage router and began in 2001. Luter and his team migrated shortly thereafter to redundant SN5428-2s in both datacenters.

Note

Cisco Systems, Inc. announced the "end of life" of the Cisco SN5420 storage router in May, 2003. Although the product will be supported until 2007, Cisco encourages its customers to upgrade to the SN5428-2.

Most recently, however, Luter and his team purchased a Cisco MDS 9506 Multilayer Director SAN switch, and are currently in the process of migrating the environments from the SN5428-2 to Gigabit Ethernet IP Storage Services Modules on the 9506. Additionally, Luter and his team are evaluating the use of both iSCSI and Fibre Channel over IP (FCIP) as viable transport solutions for long-distance replication between both locations.

Total Cost of Ownership

Considering the nature of the environment at the CTRC (relatively small total storage requirements with moderate growth and high utilization rates), the financial savings associated with storage networking at the CTRC stem not from the migration of DAs to networked storage, but primarily from investment protection via the increased utilization of the IP network backbone.

With a mix of roughly 75 percent SAN and 25 percent DAS storage, and allocation efficiency rates of roughly 90 percent, Luter and his team stand to achieve only a relatively small ROI by migrating the remaining 25 percent DAS to networked storage or by increasing the allocation efficiency to 100 percent. For the time being, the additional 10 percent of unutilized storage is held as a buffer, the loss of which can cause a significant decrease in productivity.

The use of the Cisco IP backbone to transport block data between campuses boosts the utilization of the network infrastructure, which increases the value provided by networking capital expenditures; in this case, it is a pair of redundant Cisco Catalyst 4506s. In addition to storage support, the IP backbone provides transport for both voice and internetworking. Transport is just as much an asset as the storage components, and increasing the utilization of any asset serves to lower the TCO for the entire infrastructure.

Therefore, the addition of the SN5428-2 (to be replaced in the near future with IP Storage Services Modules configured on the Cisco MDS 9506) creates only a slight increase in the storage-related TCO, which is more than offset by the decrease in the overall TCO.

Including the cost of backups, which are completely tape-based, the TCO for storage at the CTRC is $0.036 per MB. Backup costs at the CTRC, based on a rotation of weekly, monthly, and incremental backups average just over $43,000 for a one year period and represent roughly 10 percent of the overall storage infrastructure TCO.

With only two staff members dedicating 40 percent of their time each on storage-related initiatives, and no contract or temporary laborers on staff, FTE costs for supporting the 13.6 TB of storage at the CTRC are relatively insignificant. Maintenance charges for the majority of the storage components are not a factor because most of the hardware is still under warranty and maintenance charges are reflected in the purchase price for the storage for the first three years of ownership. Raw storage acquisition costs then, exclusive of the Fibre Channel infrastructure (switches and host bus adapters [HBAs], are still the leading component costs contributing 51 percent to the TCO.

Network infrastructure costs, on the other hand, represent only about 2 percent of the overall costs. Although Fibre Channel components, including the Cisco MDS switch, make up 14 percent of the TCO, if the CTRC opted for a more complex and more costly SAN extension infrastructure, the costs would have more than doubled. In addition to capital cost savings, the CTRC also benefits from the lack of a learning curve associated with migrating to a different SAN extension solution. Because iSCSI traffic travels over the campus IP backbone, the storage network can be managed by the same networking team that supports the CTRC's IP telephony infrastructure, creating more economies of scale.

The chart in Figure 6-2 highlights the percentage each component contributes to the overall cost of storage infrastructure at the CTRC.