What to consider in a departmental SAN

If you're the IT manager at a remote site or branch of a larger company and you've been managing your storage via a direct-attached storage (DAS) model, at some point, you may have gone to the till and proposed a storage-area network (SAN).

If the powers that be gave you a thumbs down, it may have been for any one of a variety of reasons, ranging from initial equipment costs and "It's not necessary, and we can't afford the additional staffing expertise it requires," to (perhaps the most painful of all) "Why should we spend that type of money just to make your life easier?"

So you limped along, adding drives to servers and sweating bullets about your backup window, LAN congestion and data availability.

A new assortment of elements coming into alignment might make it worthwhile to re-evaluate your storage strategy and go back down the hall to propose a "departmental SAN." You might not get such a chilly reception this time.

CFO: Friend, not foe

If you're working for a publicly held company, your CIO and chief financial officer are already attuned to the storage requirements posed by the Sarbanes-Oxley Act that take effect in November. FYI: There is actually a slew of legislative initiatives influencing storage practices, but outside of Sarbanes-Oxley, most of them target the information practices of financial and banking institutions or health care and government concerns. As an IT manager, technology (rather than compliance) is of course your true domain, but it's never a bad idea to be aware of such developments.

In terms of things that are less tangential to your function in life, yet are still near and dear to your CFO's heart, the prices of small SANs have come down so drastically in the past year (and even more so in the past three to six months) that the same capabilities you proposed two years ago for US$60,000 to US$100,000 in initial capital outlay can now be achieved for under US$20,000. In fact, starting prices for some fairly powerful entry-level Fibre Channel SAN systems from major storage providers are now dipping below the US$10,000 mark.

In addition to Fibre Channel, a new wave of iSCSI-based solutions is on the horizon. ISCSI uses standard TCP/IP network gear to connect storage, providing a level of familiarity and allowing software-based systems that provide low-price (albeit lower-performance) entry points.

Beyond ongoing competitive pressures influencing the pricing of storage networking gear, a new market phenomenon has been responsible for driving small SAN pricing down to its current level -- the rapidly growing small and midsize business SAN market. Potential departmental SAN users are now indirect beneficiaries of this phenomenon because, aside from the issue of connecting to the enterprise SAN that's undoubtedly already in place at corporate headquarters, the hardware configurations and storage requirements for department entities and for small and midsize businesses have much in common. And the simplicity of implementing and managing new SANs designed for small and midsize businesses plays into departmental SAN acquisitions as well.

What comes next? The departmental SAN vs. DAS decision

Curiously, the definitions attached to various SAN types (departmental SANs are technically "10 servers or less") often create gray areas instead of lines of distinction that are practical in helping you make best-practices decisions. Actually, gray is good because, ultimately, whatever you decide to implement needs to be an outgrowth of your own particular storage and business application requirements -- present and future -- and be flexible enough go where your business needs take it. You can scale a departmental SAN well beyond 10 servers and, by contrast, a server count of five doesn't mean you won't benefit from a departmental SAN. Nor is the SAN vs. DAS question purely related to raw storage-capacity needs.

In terms of questions that will help decide whether to stay with a direct storage model or move to a departmental SAN, here are a few key ones that IT managers can ask to get started:

  • How fast is your storage growing, and how often are you adding capacity to existing servers or adding new servers?

  • Are some of your servers nearing capacity, while others are underutilized? Is the process of upgrading or replacing your servers time-consuming or disruptive?

  • How many servers are you supporting, and how much are you paying out in server licensing fees annually?

  • Do your users desire access to various storage pools?

  • Are your backup windows becoming increasingly narrow?
If your storage capacity growth rate is requiring you to regularly add drives to existing servers, it won't be long before you eventually outstrip your server capacity. Adding servers due to capacity issues (especially while some servers remain underused) means increased support time and paying additional licensing fees, both of which are temporary fixes in the end. The occurrence of these situations in a DAS environment points to cost savings and better business continuity from a small departmental SAN.

In addition, you'll find that decoupling your servers from your storage via a SAN simplifies server upgrades and replacement. Beyond these basics, business application needs enter into the equation. For example, while even a server count of two with room to grow in terms of capacity could theoretically require a SAN, you may be doing just fine with DAS. But once you move beyond five or more servers, you should probably look into a SAN. Similarly, if backup procedures are getting increasingly elongated, and access to storage currently isolated on different servers is requested by users, time and money could be saved by moving to a consolidated storage environment.

The iSCSI vs. Fibre Channel question

Business applications will ultimately play the strongest role in what type of storage network you deploy as your location's first SAN. Vendors in both the iSCSI and Fibre Channel camps realize that absolute simplicity in deployment and ongoing management is a requirement for all first-time SAN users.

An iSCSI SAN applies your existing knowledge of the Ethernet protocol and can be an answer to the issues posed by a DAS -- as long as you don't overextend it and you deploy it in an environment where performance isn't a concern. A branch or campus of a bank, for example, wouldn't be a great environment for an iSCSI-based departmental SAN due to transactional performance requirements. A business where information flow isn't the lifeblood of the company would probably find iSCSI performance suitable for its needs. Fibre Channel SANs, on the other hand, deliver better performance, but they've historically been regarded as complex and expensive. Some of the new entry-level Fibre Channel SAN solutions have been designed to be installed and maintained by users without Fibre Channel experience.

Low-cost storage area networking solutions suitable for first time users looking to alleviate the technical limitations, costs and support issues associated with DAS environments are quickly making their way into the marketplace.

Mike Kane is director of product marketing at Emulex, a US based vendor of Fibre Channel host bus adapters and other products for storage networking systems.

Join the newsletter!


Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.

More about DASEmulex

Show Comments