Every storage area network (SAN) will inevitably grow to keep pace with the changing needs of enterprise storage. Growth certainly implies more storage capacity -- usually through the adoption of more or larger disk arrays -- but raw capacity is just the beginning. Growth also means meeting the demand for improved SAN performance with larger switches and enhanced host bus adapters (HBAs). Superior storage resource management (SRM) and capacity planning both play an increasing role in SAN growth, allowing more efficient acquisition and utilization of enterprise storage. This Buying Guide is intended to help clarify the principle considerations involved in any SAN upgrade purchase and offers a set of product specifications that can help readers identify prospective new upgrade products. Before we look at specific upgrade categories, let's start by identifying the core concerns for any SAN upgrade.
Identify the problem. In order to deploy an effective upgrade, it's crucial to start with a clear understanding of any problems or limitations with the current SAN. Most SAN upgrades are performed to add storage in the form of new disks or more arrays. Another common problem is impaired performance or bottlenecks. A less obvious problem is "lack of insight" into the SAN because administrators cannot monitor storage capacity or efficiently optimize storage utilization. Understand "why" an upgrade is necessary and have tangible data available (wherever possible) to strengthen your upgrade justification.
Set objectives for the upgrade. This is a close corollary to the first point. Once you determine the problem, it's important to set an upgrade goal. For example, it's not enough to simply "add more bandwidth" to overcome a bottleneck. Know how much additional bandwidth is really needed to deal with the problem and factor in adequate "headroom" to accommodate a reasonable amount of future growth. By setting a measurable goal, it is much easier to gauge the upgrade's initial success and compare your estimated growth to the SAN's actual growth demands over time, allowing better estimates in the future. For example, suppose that you currently manage 10 terabytes (TB) of storage, which has been growing at 50% each year. Your storage upgrade objectives may be to add another 5 TB of storage this year and budget another 8 TB of storage for the following year. Breaking up this upgrade into quarterly acquisitions can also help to ease the burden of huge capital expendatures.
Look beyond the lowest price. Rather than opting for the least expensive upgrade, consider the best "effective" price for a product that addresses all of your needs, but omits the unnecessary bells and whistles that simply don't align with your upgrade requirements. Also, consider costs incurred after the initial purchase -- usually in product service or software support. Analysts suggest that you seek ways to reduce the cost of your ongoing service and maintenance fees as well as ongoing software support. Also look at products that offer longer warranties; even going out four or five years if you think you will use the technology that long. For example, a storage array may be priced very attractively, but require an extra software purchase (and annual license) to support snapshots. A different storage array may be slightly more expensive, but include snapshot functionality already -- making the second array a "better deal" for you.
Consider the impact of technology cycles and future redeployment options. When selecting a SAN upgrade, also consider potential avenues of redeployment for any products that are being displaced. For example, it may be necessary to perform a forklift upgrade, replacing an older storage array with a larger or newer model. However, the older array being replaced may still serve the organization as a lower storage tier, storage in a remote office or disaster recovery facility or even serve as a lab testing platform. Redeploying displaced products can sometimes help to resolve other problems in the enterprise while forestalling other capital expenditures in the process.
Upgrades usually cost less over time. Analysts note that overall storage costs (e.g., disk costs) are declining by roughly 10% each quarter. This rate of decline places administrators into a dilemma because any savings on purchases today (even volume purchases) are generally offset by lower future costs. As a rule, don't buy today what you can buy tomorrow at a lower cost. Smaller and more frequent upgrades tend to be more cost efficient, but it's important to have an accurate knowledge of growth rates and predictability in order to leverage this principle properly.
Consider the product's interoperability and/or heterogeneity. Although interoperability appears to be improving in the storage industry, it's still important to evaluate a new product to ensure that the upgrade will fit smoothly into your existing SAN hardware and software infrastructure. For example, a new SAN switch must work with your current management software tools, and a new array should be supported by your replication or virtualization software. The main emphasis is on simplification and reducing the number of tools needed to manage the storage environment, so try to avoid upgrades that will add to the storage management burden.
Evaluate the product's service and support. You may require service and support agreements to protect SAN upgrades, such as new disk arrays or new storage management software tools. For new hardware, service and support ensures that timely technical assistance is available to restore physical failures in the storage system. For new software, service and support typically provides access to telephone support and patches/updates as the software evolves. Some level of service and support is normally included with the initial product purchase, but renewed coverage can be quite costly once the initial coverage expires. As a rule, make sure that service and support is available for the expected service life of your SAN upgrade. Add the cost of any extended coverage to the total cost of any upgrade plan.
Evaluate changes to management requirements and processes. Storage practices often rely on documented procedures to ensure consistent day-to-day operations. Anytime that hardware is added or replaced, and each time that critical management software is revised or changed, established practices will invariably be impacted. When considering a SAN upgrade, it's important to evaluate how those changes will influence internal IT processes, and processes may need to be adjusted accordingly.
Consider training needs. Major SAN upgrades may involve dramatic hardware replacement, and substantial hardware changes may demand additional IT staff training. Determine whether training is needed, the number of staff that require training and the cost of training from the product vendor. In many cases, training may be included with the upgrade's purchase price, but that's not always certain. Training costs, if any, should be figured into the total cost of any upgrade plan.
This was first published in February 2007