Exchange and Outlook UPDATE, Outlook Edition—brought to you by Exchange & Outlook Administrator, a print newsletter from Windows & .NET Magazine that contains practical advice, how-to articles, tips, and techniques to help you do your job today.
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February 7, 2003 — In this issue:
- Fighting the Cluster Monster
- Don't Miss Our 2 New Security Web Seminars in March!
- Join the HP & Microsoft Network Storage Solutions Road Show!
- HOW TO: Implement Exchange 2000 Server on a Windows 2000-Based Cluster
- Featured Thread: Rehoming Exchange 2000 Public Folders
- Results of Last Month's Instant Poll: Wireless Messaging
- New Instant Poll: Exchange Server Version
4. HOT RELEASE (ADVERTISEMENT)
- ExMS Move Mailbox Manager Supports Exchange 2003/Titanium
5. NEW AND IMPROVED
- Access Exchange Server from Your PDA
- Submit Top Product Ideas
6. CONTACT US
See this section for a list of ways to contact us.
(contributed by Paul Robichaux, News Editor, [email protected])
Clustering seems to be a great idea—it promises superior availability and reliability for applications such as Exchange Server. However, I often hear administrators saying that they're "fighting the cluster monster." Does Exchange clustering truly work? To answer that question, we need to dig into the mechanics of clustering and better understand what it can and can't do.
First, understanding some basic Windows clustering principles is important. Each machine, or node, in a cluster can be in one of two states—active or passive—with respect to the cluster's application. For example, a two-node Exchange configuration can have either one active node and one passive node or two active nodes. Passive nodes are supposed to be ready to accept work from active nodes (i.e., fail over). The whole point of clustering is to be able to fail over users from one node to another without the users noticing. To that end, the Exchange and Outlook teams have devoted a great deal of effort to making Exchange fully able to use Windows' clustering features.
The nodes in a cluster share access to a set of storage devices through shared SCSI or Fibre Channel. You can divide the storage into logical volumes, each of which can be owned by one node at a time. The cluster uses a special volume called the quorum disk to log cluster configuration information and changes. The Windows cluster software can replay these changes when an offline node comes back online. The nodes in an Exchange cluster don't share data—two nodes can't write to the same mailbox database at the same time. Therefore, you must configure storage to give each node independent access to the Exchange stores and log files.
Administrators often have several complaints against clustering in general and against clustering Exchange in particular. The first is that clustering is expensive. No argument there: A low-end two-node cluster will set you back at least $15,000 for the two nodes and a storage unit (plus more for disks). You also have fewer hardware choices: You're restricted to systems listed in Microsoft's cluster Hardware Compatibility List (HCL). Don't even think about scrimping by clustering (possibly less expensive) hardware that isn't on this list. Although other systems might work, Microsoft won't support them and you'll be sorry in the end. (You can find the HCL at the URL below.)
The second objection is that clustering can actually increase downtime instead of reducing it. This complaint is also true, but its truth stems from a basic fact that has nothing to do with clustering: The most common point of failure is the administrator! Making a dumb mistake on one system is one thing. Making the same dumb mistake on a complex multinode cluster that supports thousands of users certainly increases the odds that the mistake will cause some damage. Everyone who has administrative or physical access to your Exchange clusters must understand how clusters work and how they differ from nonclustered systems. Although this necessity might require extra training, the increased uptime you'll gain from a properly administered cluster will more than repay the extra time and cost.
Aside from these general complaints, Exchange 2000 Server specifically comes under fire for an architectural decision that limits Exchange active/active clusters to a maximum of about 1900 Messaging API (MAPI) users per node. Active/passive clusters, however, have no such limitation (nor do systems that don't host MAPI clients), so Microsoft recommends using active/passive clusters. The anticlustering crowd asks how you can justify spending double the money for a two-node cluster that provides only one active node. The answer is simple: Clustering still provides a terrific way to perform rolling upgrades or maintenance—-planned or unplanned—-without interrupting users' work. Properly designed and maintained, Exchange clusters will indeed deliver the increased uptime that Microsoft promises. And although the recommended configuration for an Exchange Server 2003 (formerly code-named Titanium) cluster is still an active/passive "N+1" or "hot-standby" setup, an Exchange 2003 cluster (running on Windows Server 2003) can support as many as eight nodes, only one of which must be reserved as a failover target.
Next week, I'll delve into some design principles that you need to know to build a cost-effective Exchange cluster. In the meantime, I'm going to battle the real monster: the temptation to ignore my column deadlines in favor of the Xbox in my workroom.
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Each week, Microsoft posts several Exchange Server how-to articles to its Knowledge Base. This week, learn about Exchange 2000 Server implementation on a Windows 2000-based cluster, from an Exchange 2000 viewpoint.
After building a second Exchange 2000 Server system, lucasszy is trying to rehome public folders from an original Exchange 2000 machine to the new machine (ultimately keeping both machines running). However, replication is incredibly slow. To offer your advice or join the discussion, go to this URL:
The voting has closed in the Exchange & Outlook Administrator Web
site's nonscientific Exchange Instant Poll for the question "Do you provide wireless messaging to users?" Here are the results from the 223 votes:
- 26% Yes - 18% Not yet, but we plan to do so within the next 12 months - 56% No, and we have no plans to do so
(Deviations from 100 percent are due to rounding.)
The next Exchange Instant Poll question is, "What version of Exchange Server do you currently run?" Go to the Exchange & Outlook Administrator home page and submit your vote for a) Exchange Server 5.5 on Windows NT, b) Exchange Server 5.5 on Windows 2000, c) Exchange 2000 Server, Standard Edition on Win2K, d) Exchange 2000 Server, Enterprise Edition on Win2K, e) Exchange Server 5.5 and Exchange 2000 Server (mixed-mode) on Win2K.
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5. NEW AND IMPROVED
(contributed by Carolyn Mader, [email protected])
Equisys released Zetalink 3.0, software that lets remote workers securely access corporate messaging and groupware functions from mobile phones and PDAs. Zetalink provides mobile employees realtime access to Outlook and Exchange as well as remote access to Customer Relationship Management (CRM) and finance applications. For pricing, contact [email protected] or 770-772-7201.
Have you used a product that changed your IT experience by saving you time or easing your daily burden? Do you know of a terrific product that others should know about? Tell us! We want to write about the product in a future Windows & .NET Magazine What's Hot column. Send your product suggestions to [email protected]
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