Tip

How to evaluate and purchase a SAN

Martin Taylor, Converged Network Manager, Royal Horticultural Society
If the time has come to purchase your first SAN, there are many challenges to overcome before you can reap the benefits of centralized storage.

Some of the decisions facing prospective SAN purchasers can mean the difference between deploying a storage system that opens up new opportunities or ending up with a very expensive anchor holding back the organization.

There are many elements in the SAN purchasing process. Let's look at the ones that can help you specify a system to meet your organization's goals.

Business goals, tech specs

The starting point in a SAN purchasing strategy is to determine the business' needs -- both present and future -- in terms of data management and storage. The first step is to hold assessment meetings with those areas of the business that use the SAN in order to create a picture of the organization's storage requirements for the next three to five years.

A key part of the process is to determine which SAN technical specifications are needed to meet the organization's goals. For example, if you will be running a database-centric system, you will need to determine the disk access speeds required to guarantee performance levels. At the same time you may want to specify advanced LUN masking features to optimise disk access times for those applications.

If disk cost and power consumption are issues, you may need to look for a SAN that allows intelligent disk tiering and data migration. You will also need to consider

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the backup options available to safeguard your data and how quickly the system can be restored in a disaster recovery situation.

If the SAN is intended to form the heart of new working practices for your organization -- for example, as a backbone for server virtualization – you will need to think about different requirements. These include the ability to boot virtual servers directly from the SAN itself and apply thin provisioning to grow virtual drives intelligently, such as is available from manufacturers such as Compellent Technologies and 3PAR.

Evaluating SAN vendors

Once you have determined the relevant business goals and the technical specs, you can begin the vendor evaluation process. Many SAN vendors and SAN resellers offer free educational seminars that showcase different systems and provide Q&A sessions with industry experts.

Attending these events allows you to build up a portfolio of system knowledge for later comparison and can provide a much broader view of the SAN marketplace. Unleashing the office techies to attend this type of event then letting them present their findings will yield a surprising return when it comes to seeing past the sales pitches and making sure any prospective system is fit for purpose when it is time to make a decision.

Many organizations that are already SAN users are willing to open their doors to prospective purchasers through reference site agreements with manufacturers and resellers. Visiting these sites can be worthwhile if you can talk directly with the storage administrators who have experience using the SAN ... preferably away from any sales representatives. Such discussions can illuminate any pitfalls that may be awaiting you post-purchase and show up any gaps in after-sales services offered.

Making sure your prospective SAN supplier has the resources to fully support the product throughout the lifecycle of the product is vital to your purchasing strategy. A minimal level of after-sales support must include comprehensive hardware replacement strategies and round-the-clock availability of technical support. My experience of "telephone tennis" with foreign call centres was a big influence on my choice of support services from potential suppliers. The ability to speak to knowledgeable staff with remote access to my SAN was a big factor in our eventual selection of a SAN from Compellent and its Co-Pilot service for the Royal Horticultural Society.

When the purchase is imminent, a full due diligence examination of the successful supplier is also advisable. A supplier in financial or legal difficulties is unlikely to provide the service levels required for this type of product and could fail to honor support contracts.

Staff skillsets

The requirements for administering the SAN are another important factor. If you have a dedicated and qualified SAN administrator, this is a moot point. However, if SAN administration is to become part of the job function of an existing member of staff, then a full assessment of the skills and training required to manage the technology should form a part of the purchasing process. The newest SAN products use a Web browser-style management GUI that allows existing staff with a solid knowledge of traditional server RAID array disk management concepts to adapt quickly to a SAN administration role.

To summarize, the main objective when purchasing a SAN is to ensure that it meets the needs of your business at the point of purchase and throughout its lifecycle as a useful component of your business. To attain this objective, you need to know the driving goals and processes of your organization and the technical specifications available from SAN products that can meet them.

At the Royal Horticultural Society we collated all this into a decision matrix which scored potential vendors' products against our need for storage with fast and reliable image search and retrieval through an SQL database to help us make that decision.

Martin Taylor is a converged network manager with the Royal Horticultural Society, which recently went through the process of buying and implementing a Compellent SAN as a repository for its library of 200,000 images.

This was first published in August 2009

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