Editor's Note: Welcome to SmartAdvice, a weekly column by The Advisory Council (TAC), an advisory service firm. The feature answers two questions of core interest to you, ranging from career advice to enterprise strategies to how to deal with vendors. Submit questions directly to [email protected]
Question A: When is it appropriate to use each of the various storage-attachment technologies?
Our advice: There just never seems to be enough data storage available, so you have to consider when it's appropriate to use each of the various storage-attachment technologies. Vendors have responded to this need with a confusing variety of products--direct-attached storage, network-attached storage, storage area networks, and Internet Small Computer System Interface, or iSCSI. Your company's particular mix of storage-attachment technologies should be based on specific requirements for economy, speed, ease of use, and storage-management tools.
Direct-attached storage is the original method of attaching storage devices to midrange computers and PCs. Rather than through a network, it's physically connected to a computer by a variety of standard interfaces, including Advanced Technology Attachment and Integrated Drive Electronics, two PC disk-drive technologies, along with Serial ATA and SCSI connections. For companies with only a few servers and limited storage needs, direct-attached storage is a proven technology that's simple, secure, and economical, with system capacities that range up to 4 terabytes. The disadvantages are poor data protection and limited growth options.
Storage area networks are attached to servers through high-speed Fibre Channel networks, delivering the performance needed for data-intensive applications. Their modular designs and high capacities (hundreds of terabytes) allow for security, scalability, and redundancy, but they have limited wide area networking capabilities, and Fibre Channel hardware is relatively expensive.
The latest entry in storage attachment is Internet Small Computer System Interface. Like network-attached storage, iSCSI uses IP networks, but optimizes device access by sending highly efficient, standard SCSI commands over the network. Depending on your performance needs, iSCSI devices can be configured either on a dedicated IP network or through the company network. Since IP networks are ubiquitous, iSCSI offers the promise of truly location-independent data storage and retrieval. The technology is gaining popularity because of its low cost, high speed, and sophisticated management tools.
The type of data storage that you choose is going to depend on your specific requirements. Network-attached storage and direct-attached storage will maintain their low-cost niches for workgroups and smaller companies. Expect to see iSCSI gain popularity at the expense of Fibre Channel SANs, because it offers the best of both network-attached storage and storage area networks--scalability, flexible architecture, access speed, and management tools--at a much lower cost.
Question B: What issues must we address in planning a migration to Microsoft Exchange 2003?
Our advice: You're not alone in still being in the planning stage of your migration to Exchange 2003. It's been estimated that, as of year-end 2004, 40% of Exchange mailboxes are still on Exchange 5.5, 43% are on Exchange 2000, and only 14% are on Exchange 2003.
Messaging is a critical application in almost all organizations. It's imperative that your migration be seamless and transparent to both your internal users and external correspondents. If there's an interruption, you'll hear about it right away. Migrations can cause serious outages if you don't plan carefully.
Messages between Exchange and a "foreign" system are typically handled by Exchange Connectors. Exchange provides a suite of connectors to handle just about any non-Microsoft messaging system. A connector tricks the foreign messaging system into thinking the Exchange Organization is of the same-breed mail system. Exchange will use the foreign-messaging system's addressing scheme. Exchange's Connectors are well documented in the Microsoft Exchange library.
Sending mail to the Internet from both Exchange and the foreign-messaging system is usually simple. Just make sure your firewall is configured to permit outbound Simple Mail Transfer Protocol from your new servers.
Inbound Internet mail routing is the most difficult aspect of co-existence, because you will be sharing SMTP name spaces with recipients spanning both messaging systems. Most systems want to be authoritative for any SMTP name space for which they're configured to accept mail. How will the messages get from the Internet to recipients in the other system? The way you will build this depends on the migration tool you use.
Here are some other points to prepare your organization for migration:
-- Brian O'Neil
Beth Cohen, TAC Thought Leader, has more than 20 years of experience building strong IT-delivery organizations from user and vendor perspectives. Having worked as a technologist for BBN, the company that literally invented the Internet, she not only knows where technology is today but where it's heading in the future.
Brian O'Neil, TAC Expert, has more than 10 years experience in IT designing, migrating, and managing enterprise network infrastructures for the U.S. Department of Defense, financial organizations, medical institutions, and law firms. He has been the primary technical lead and project manager for large migrations to Microsoft Active Directory and Exchange 2003.