Applications Server

Designing and Optimizing Storage in an Exchange Server 2007 Environment (part 1) - When Is the Right Time to Implement NAS and SAN Devices?

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1/14/2012 4:04:43 PM

Defining the Technologies

To understand how and when to use technologies such as NAS or SAN, it is important to understand what they are and what they offer. The technologies differ in how they are used and what advantages they provide. Many administrators assume that they need a SAN when often a NAS will suffice. Because information technology (IT) budgets are far from limitless, it is to your advantage to know that you aren’t overbuying for your solution. By the same token, it is often less expensive to buy your solution all at once rather than trying to expand it later.

What Is a SAN?

A SAN is a high-speed, special-purpose network or subnetwork that connects various data storage devices with associated data servers on behalf of a larger network of users. Typically, a SAN is but part of an overall network of computing resources for an enterprise. A SAN is usually located in relative proximity to other computing resources such as databases and file servers but might also extend to remote locations for backup and archival storage. These remote locations are traditionally connected via wide area network (WAN) carrier technologies, such as asynchronous transfer mode (ATM) or Synchronous Optical Networks (SONETs).

It is very important to understand that the SAN is more than just the chassis that contains the disks. It includes the redundant array of inexpensive or independent disks or drives (RAID) controllers for the disks, the Fibre Channel switching fabric, and the host bus adapters (HBAs) that reside in the data servers. SANs are traditionally connected to hosts via Fibre Channel and talk via Fibre Channel Protocol. Although it can be fairly easy to support dual-arbitrated fiber loops in a corporate environment, keep in mind that one of the primary benefits of SAN is the ability to do block-level mirroring to another SAN. If this SAN is located remotely, up to 1,000km away with current fiber technology, a company needs to have fiber between the two locations. A fiber connection across those kinds of distances can be quite expensive.

SAN technologies excel in the area of disk performance. Fibre Channel networks regularly push 4Gb/sec of throughput. Although SCSI technologies can move data at up to 320Mb/sec and can be bonded together for higher throughput, they are limited to less than 25 feet of distance. SAN, not unlike SCSI, is seen by the host system as raw disk space. This is also referred to as a block-level technology. In the past, database applications required block-level access to the disk as well as the “near 0 latency” offered by SAN.


Although most SAN manufacturers refer to the performance of their products as having zero latency, it is important not to misinterpret this. Zero latency refers to the fact that Fibre Channel has extremely low overhead and doesn’t add additional latency. The laws of physics, on the other hand, are still in effect. A 1,000-km fiber run between remote locations still takes 7 milliseconds round-trip.

What Is NAS?

NAS is a hard disk storage technology that uses an Ethernet connection rather than being attached directly to the host computer that is serving applications or data to a network’s users. By removing storage access and its management from the host server, both application programming and files can be served faster because they are not competing for the same processor time. The NAS device is attached to a local area network (LAN) via Ethernet and given an IP address. File requests are mapped by the host server to the NAS device.

NAS consists of hard disk storage, including multidisk RAID systems and software for configuring and mapping file locations to the network-attached device. NAS software can usually handle a number of network protocols, including Microsoft’s Internetwork Packet Exchange, Common Internet File System, and NetBEUI; Novell NetWare Internetwork Packet Exchange; and Sun Microsystems Network File System. Configuration, including the setting of user access priorities, is usually possible using a web browser though many NAS offerings require command-line configuration. Most NAS manufacturers include specialized software for allowing specific applications such as Structured Query Language (SQL) or Exchange to take advantage of special functions provided by the NAS. These functions include things like mirroring, failover, automated recovery, and snapshotting.

NAS has the advantage of using existing Ethernet technologies that are much less expensive than fiber technologies. With the availability of 10Gb Ethernet, NAS is able to compete with Fibre Channel–based technologies even with the added overhead of Ethernet over Fibre Channel. In most scenarios, Gigabit Ethernet is sufficient for Exchange 2007 servers, especially if multiple connections are employed.

When Is the Right Time to Implement NAS and SAN Devices?

There are many reasons to implement a NAS or SAN solution in favor of direct attached storage. In the case of Exchange 2007, if the requirements for storage consolidation, reduction in mailbox server count, centralized management of disk resources, service level agreement (SLA) recoverability times, or near real-time mirroring of data justify the cost of a SAN or NAS solution, it is time to explore those options. To make an informed decision about when to make the switch within your Exchange 2007 environment, it is important for you to pass through several phases:

  1. Analyze— Gather usage metrics and performance metrics. Determine how storage is being used and how it affects the business processes. Determine if disk throughput is the bottleneck in your Exchange deployment.

  2. Plan— Determine the current limitations of your storage solutions. Prioritize the problems and determine if there is a better way. Don’t fall into the trap of doing things just because they were always done a particular way.

  3. Develop— Build the proposed solution for testing. Perform benchmarking to show improvements over the old methods. Experiment with various functions of Exchange 2007 on different types of disks. Get a feel for the improvement versus the costs.

  4. Pilot— Test the solution and improve it based on user feedback. Educate the user population on how to take full advantage of the new functions and determine the improvements in efficiencies.

  5. Deploy— Deliver the solution to the masses.

Following this methodology not only streamlines the process of implementing new and more efficient storage technologies, but also provides valuable data to help upper management buy into the upgrades and support the storage program for the Exchange environment.

Analyzing Your Storage Needs

The first phase of any good project is an in-depth analysis of the environment and its needs. In the case of storage systems, it is critical to identify any systems with special requirements. This includes systems that require multiple layers of redundancy, systems that are under extremely tight SLAs, and systems that cannot tolerate a loss of data. In the case of Exchange 2007 that is deployed by role, it is most likely only the Mailbox server role that will benefit significantly from using SAN or NAS technologies. Similarly, you might determine that it is less expensive to take advantage of the additional memory that can be used by Exchange 2007 because of its 64-bit architecture, to increase the caching of database transactions and, therefore, reduce the necessary number of disks. NAS and SAN solutions can be very expensive compared to purchasing memory for a server.

Another key area to understand is the capacity requirements of the enterprise. If an investment is going to be made in storage, it is a good idea to plan for several years of growth. Look at the number of servers in the environment. If additional servers have been added simply because that is the way things were always done, it is time to look at shifting the philosophy to doing things because it is the right way to do it.


Disk drives get larger, faster, and less expensive each year. When planning for the future, keep expandability in mind. By buying a partially filled chassis now and adding additional disks later, you can take advantage of falling disk prices and save money over the long run and still get the full capacity they need and the benefits of fewer chassis.

Planning the Storage Solution

Storage technologies can be very confusing. In most situations, valid arguments can be made for using any of the available technologies. This is a situation in which it makes a lot of sense to get your vendors involved. Contact your potential vendors and let them know what your storage requirements are. Often, they have worked with other companies with similar needs and can provide valuable insight into what worked and what didn’t. Given the costs of a large storage system, you can’t afford to do it wrong.

After you have an idea of what you want to implement, find out if you can contact references to determine if they were happy with the solution they implemented. Some companies try to get you to commit to the latest and greatest versions of their software and firmware. Large storage environments are a big investment and business processes depend heavily on it. Ensure that you are implementing a stable and well-tested solution.


A tremendous number of options are available when it comes to storage solutions. When in doubt about a decision, always refer to the original goals of the project and ask yourself, “Does this decision support the goals of the project?”

Developing the Storage Solution

After you have determined the needs, explored the options, and come up with a plan, the real fun can begin. Any solution that will become part of the critical path of business must be developed and tested in a controlled lab environment. This is the part of the project where policies and procedures start to take form. Practice runs of mirroring, failing over of resources, and recovery of systems ensure that the solution will be able to support the needs of the company.

During this development phase, practice connecting your servers to the SAN or NAS. Develop and document standards around HBAs or network interface cards (NICs), the versions of firmware that will be used, and the version of the drivers that will be used. Most SAN and NAS manufacturers provide a detailed list of supported combinations of hardware, firmware, and software. Deviate from these approved lists at your own risk. The last thing you want to implement is an unstable storage environment because you chose not to follow the recommended configurations.

The development phase will identify several requirements that are not usually thought of during the planning phase. Most specifically, these requirements are in the area of facilities. Most SAN devices are fairly large. An EMC Symetrix and Connectix, for example, will take up a full rack each. With heat generation more than 3,000BTUs, HVAC resources will need to be considered. Also keep in mind that most SAN and NAS solutions require 220V to run them. Ensure that planned data center locations have appropriate space, cooling, and power. Power should include not only the standard AC feed, but battery backup as well. Be aware of any special requirements of the SAN or NAS. Some SAN devices on the market void their warranty if they are placed within 5 feet of any solid objects.


Be sure to carefully document the entire installation and configuration process. It not only makes troubleshooting easier, but it also provides the full road map for pilot implementation.

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