SAN Buyers Guide: Part II Page 3


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New Capabilities For Disaster Recovery (DR)

The separation of storage from the servers provides an opportunity to plan for recovery with better optimization for data, and also to manage data and processing separately. In order to create multiple copies of critical data in other parts of the SAN, data replication can be applied to storage (at the controller level, switch level, or OS level). Also, appropriate levels of protection can be applied, since specific datasets and relational database management systems (RDBMS) can be targeted according to the value.

Options For On-line Recoverability

According to recent storage industry estimates, about 80 percent of Fortune 1000. companies will implement replication-based backup methods for 20 percent of their data. Moving critical data to near-line or on-line areas for very fast restore, will require increased scalability and replication methods that can be found in some SAN topologies.

Data Path Availability Improvement

SAN and advanced storage options can increase the value of availability to the business; as well as, enterprise operations costs. The improvement value of having data more available to the enterprise can be factored into a business case for SANs.

General-Purpose UNIX. And Microsoft.Windows NT. Servers Reduction

Much of an enterprise's Windows NT growth can be attributed to servers (up to 20 percent) that are installed for disk capacity only, not CPU cycles. This phenomenon is not as prevalent in UNIX environments. You can expect to see situations in which servers are acquired for the sake of storage only as server growth continues. Thanks to the centralization that is enabled with the SAN, because the assumption here for this case, is that some percentage of Windows NT servers will not need to be procured. This projected number of servers that could be avoided is multiplied by the current or projected cost per server and shown as hard-dollar savings.

Avoid Upgrades: Improve LAN/WAN Performance

If data movement, backup, and replication is migrated to the IP backbone (assuming incremental data growth), network infrastructure will need constant upgrades (about every year). New FC SAN topologies off-load the traffic to the new storage infrastructure, thus relieving the network load and potentially deferring upgrades. Thirty percent of LAN traffic can be attributed to backup processes occurring over the net. You should be able to determine how many new sub-nets or virtual private networks (VPNs) will be required to support server-to-server transfers and network-based backup from projections on server growth. You can also determine the costs of new sub-nets (network interface card (NIC), hubs, and routers) from the projected growth. And, some portion of these costs can be counted as savings when avoided in favor of FC-based topologies.

Backup Servers Reduction And Elimination

Finally, there may be a specific instance in which to reduce dedicated backup servers that are servicing small sub-nets or groups of servers. Within advanced storage architectures, the role of dedicated backup servers is likely to continue, but the need for numerous small servers is diminished. By using larger pooled storage with tape connections to silos and bypassing the need for host processing (LAN-less backup), this function will determine how the need for small, dedicated backup servers can be reduced or prevented.

Summary And Conclusions

The results can be very subjective in any ROI analysis. There are no guarantees to the models, parameters, assumptions, and payback performances discussed in this Parts I and II of this article. SAN technology should not be considered on cost savings or strong ROI expectations alone. SAN is a business-enabling technology, which, when planned and deployed correctly, can have a tremendous impact on data management, growth, performance, and investment protection. There are opportunities for SANs to impact enterprise operations and expenditures financially in the future, but these should be secondary to SANs' capabilities to help companies achieve business and operational goals.

In order to determine the best ROI results, trade-offs on values and parameters (conservative to aggressive) can be made within the spreadsheets, and the calculations run again. Summarizing savings by year and by category is the overall approach. Separation of soft-dollar savings and hard-dollar savings is highly recommended.

It is concluded that when choosing and implementing a long-term pooled storage strategy, that early cost and TCO planning in the design work is a valuable process to employ. In topology and design decisions, ROI is not the only determinant. Also, in any logical or physical pooled storage design, there are dozens of factors that need to be included. Some of the other technical and business considerations may include:

  • Availability needs for the data.
  • Chargeback costs to storage users.
  • Geographic considerations of the servers, storage and staff.
  • Improvements in data restoration.
  • Performance requirements.
  • SAN infrastructure serviceability and maintainability.
  • Scalability and non-disruptive upgrades.

Finally, SAN ROI and TCO are important elements to consider in parallel with other design qualities. Before the design is committed to production, each topology has differing cost and payback characteristics that need to be explored.

So, after hearing all of the business case reasons why your enterprise should leave the safety of their DAS environment and move to a their first SAN, what is you decision in this matter? Do you think they should move? Of course they should, but only if the right process of choosing a vendor is followed; and, that can only be determined by vendor consolidation. In other words, pooled storage architectures can consolidate the number of vendors involved in providing infrastructure services. This reduced overhead impact can be measured and summarized. But, only time will tell!

About the Author :John Vacca is an information technology consultant and author. Since 1982, John has authored 36 technical books including The Essential Guide To Storage Area Networks, published by Prentice Hall. John was the computer security official for NASA's space station program (Freedom) and the International Space Station Program, from 1988 until his early retirement from NASA in 1995. John can be reached at jvacca@hti.net.

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