Microsoft's Exchange Server 5.5 Debuts

Osmium has many new developments

Microsoft Exchange Server 5.5, formerly code-named Osmium, joins Exchange 5.0as a 1997 release. Two versions in one year is a snappy pace for a developmentteam, especially when you consider that each release has significantdevelopments.

Version 5.0 set the scene for Exchange to become a good Internet citizen,and Exchange 5.5 completes it. This newest version completes the support of allmajor Internet protocols, giving Microsoft strong leverage against competingproducts, such as Netscape's SuiteSpot family of server products.

Although increased Internet protocol support is a noteworthy development,the most important evolution in Exchange 5.5 is its upgraded internalstructures. These structures begin to accommodate the demands of massive,robust, reliable messaging servers. In short, Exchange 5.5 provides the type ofsystem you'd want to use for mission-critical applications.

Exchange 5.5 has a few weaknesses. For example, its groupware capabilitiesare still not as well developed or functional as those in Lotus Notes. Inaddition, out-of-the-box Exchange administration tools continue to focus on theneeds of small- to mid-scale installations rather than large-scale distributedenvironments. Despite these weaknesses, Exchange 5.5 is a superior messagingserver that third-party software developers can build on.

Exchange 5.5 runs only on Windows NT 4.0 Service Pack (SP) 3 or higher. So,if you're still running NT 3.51, you need to upgrade. (For information onupgrading, see the sidebar "Upgrading Is Relatively Easy," page 169.)In fact, because Exchange 5.5 supports only Windows NT 4.0, it is the firstExchange release that forces NT 3.x administrators to upgrade their operatingsystem. This fact might delay some administrators from implementing Exchange5.5.

Table 1 lists Exchange 5.5's new features. I examined these features whenMicrosoft provided Release Candidate 1 (RC1) build 1664.5 in early September1997. I've been running RC1 on both Intel and Alpha processors since itsrelease. I have been impressed by its reliability and relative freedom frombugs.

I compiled the features in Table 1 into several differentcategories: scalability, systems administration, interconnectivity, clients,enabling technology, and miscellaneous. Here's a detailed look at some of thefeatures in these categories.

Scalability: Massive Information Stores
Vendors' claims about the number of users that a server can support oftenamuse me. If you want to truly assess a server's scalability, ask the vendorseemingly mundane, yet essential, questions, such as:

*How much disk space is available on the server?

*What happens when a server fails?

*How many users will a failure affect?

*How can I restore a user's mailbox or a deleted item from a private orpublic folder?

*How much time do system backups take?

The vendors' answers are much more useful than their claims about thenumber of users. For example, if you ask Microsoft these questions aboutExchange 4.0 and 5.0, you learn that both support only a maximum 16GB ofstorage. If a server goes offline, users must stop working and cannot resumeuntil it is back online. In addition, restoring a mailbox or memo takes manyhours.

If Microsoft answers the same questions for Exchange 5.5, the answers arequite different. Exchange 5.5 has unlimited storage. If a server goes offlineand the system is part of a cluster, users experience only a brief delay. Andthanks to deleted-items caching, performing a system restore to retrieve amailbox or deleted memo is a task of the past.

Exchange 5.5 has an information store that you can theoretically expand toa massive 16TB of storage. In fact, Microsoft stopped using the 16TB numberbecause it's so vast that it's meaningless. Instead, Microsoft states thatExchange 5.5 has unlimited storage, which is an accurate statement given thedisk technology available for NT today.

Although Exchange 5.5 has unlimited storage, I find it slightlydisappointing that the information store remains one big physical file. I wouldprefer that the store be logically split across multiple arrays (especially assizes move into the 50GB to 100GB range) because of the size of disks andlimitations on I/O performance. Most large servers are not CPU-bound, whichleads to bottlenecks in the I/O subsystem. But advocates of single-filedatabases hold that this architecture is more efficient than the alternatives.They contend that single-file databases support single instance message storage,whereas splitting the information store across multiple databases results induplicate copies of messages.

Exchange 5.5 features an aggressive memory management scheme. Instead ofstatically allocating buffers, Exchange 5.5 releases buffers to the operatingsystem as required. This approach makes the server more responsive to differentsystem loads and removes many of the reasons for running the ExchangePerformance Optimizer utility.

Microsoft also improved Exchange 5.5's data flow out of the store. Becausespeed is critical when you're dealing with very large databases, Microsoftwanted to reduce backup times. If you use the most powerful parallel tape backupdrives available with Exchange 5.5 (for example, a Quantum 700 dual striped DLTdevice), you can expect to back up data as fast as 25GB per hour--a more thanacceptable rate. Slower tape drives will inevitably struggle to matchever-expanding stores, so now is the time to look at the backup hardware youuse.

Scalability: Support for MSCS
Resilience and redundancy are important in any server, especially in largeones that you can create with unlimited storage. To help ensure resiliency andredundancy, Exchange 5.5, Enterprise Edition (Exchange 5.5/E) supports MicrosoftCluster Server (MSCS­formerly code-named Wolfpack). No clustering softwarepreviously available for NT was totally compatible with Exchange 5.5's memorymanagement scheme. MSCS is the first clustering software to support transparentclustering of two servers into a single cluster that Exchange 5.5/E can functionon.

Microsoft is delivering MSCS in two phases. In Phase 1, which is nowavailable with NT Server, Enterprise Edition (NTS/E), two servers, or nodes, canoperate as an active/standby pair. If the active server fails, the standbypartner takes the load. Users experience only a brief delay when the switchoveroccurs. Two-node clustering marks the start of the path toward resilient massiveservers.

In Phase 2, which Microsoft plans to release in 1998, up to 16 servers willwork together in a tightly coupled environment. The servers will share resourcesand balance work among them. (For more information about clustering, see MarkSmith, "Clusters for Everyone," June 1997.

MSCS's Phase 2 offers the prospect of scalable clustering for Exchange 5.5,but this prospect won't become a reality until next year. Fortunately, Exchange5.5/E currently supports Phase 1. Two servers with similar hardwareconfigurations that have NTS/E and Exchange 5.5/E installed can service the sameset of mailboxes, public folders, and directories. However, the active serverhandles only user requests. The standby server remains passive until problemsoccur. MSCS defines both servers in a cluster group. MSCS ties usermailboxes to the group rather than to an individual member of the cluster.

The servers monitor each other over a pair of network cards that transmit a"heartbeat" between each other. When the standby server notices thatits partner's heartbeat has stopped, Exchange 5.5/E redirects users to the newlyactivated server. The backup server must start all the Exchange services (suchas the Mail Transfer Agent­MTA, store, and system attendant), a processthat might take a few minutes. Redirection for Messaging API (MAPI) clients(such as Outlook) that use remote procedure calls occurs automatically. Webclients might need to log on again if the server outage affected the IISconnection. Post Office Protocol (POP) 3 and Internet Mail Access Protocol(IMAP) 4 clients need to log on again.

Together, Exchange 5.5/E and MSCS Phase 1 deliver a high degree ofredundancy, especially for MSCS not being a finished product. This initialsupport for clustering can help you get closer to the goal of 100 percent uptimefor email servers. Apart from helping you increase redundancy and resiliency,clustering can help you with systems administration tasks, such as managing anemail system and recovering documents through deleted-items caching.

Systems Administration: Deleted-Item Caching and Recovery
Recovering deleted items was time-consuming with Exchange 4.0 and 5.0. Youhad to restore the last backup onto a server. Restoring several gigabytes ofstored information not only takes a long time, but it requires additionalhardware (unless you take the operational server offline, which is unacceptablein most environments).

Fortunately, Microsoft made restoring items much easier with Exchange 5.5'ssoft delete feature. Exchange 5.5 caches deleted items into a set of hiddenfolders inside the information store. Users can then use Outlook 8.03 torecover deleted items. (Only Outlook 8.03 has the necessary user interface tointeract with the server.) Outlook 8.03 puts recovered mailbox items in themailbox's Deleted Items folder and puts restored public folder items directly inthe appropriate public folder.

Soft delete lets the systems administrator decide when to permanently erasethe deleted items in the hidden cache by setting a default retention period. Theretention period is in terms of days, as Screen 1 shows. Note the Don'tpermanently delete items until the store has been backed up option. If youcheck this box, Exchange 5.5 will keep deleted items in the cache until you havecompleted a successful backup, even if you exceed the retention period. You canset separate retention periods for public and private information stores. Inaddition, you can override the default retention period for users who need aspecial schedule, as Screen 2 shows.

Nothing comes for free, including soft delete. When users have deleteditems in the hidden cache, those items occupy space in the information store.You can't easily quantify exactly how much additional space the hidden cachewill use because that number depends on how often users delete items from theirmailboxes and how long you want to keep deleted items in the cache. For initialplanning, you can estimate that deleted items will occupy up to 10 percent extraspace if you use a 30-day recovery period. Shortening the recovery period to 7days will reduce the additional space requirement to well under 5 percent. Thesefigures are just estimates. I based them on the assumption that the privateinformation store grows at a rate of roughly 5 percent per week. You'll findthat the additional load levels off after a couple of weeks as new items takethe place of permanently deleted items. Each system will be different, so usethese estimates as a guideline only.

Microsoft anticipates that deleted-items caching will eliminate the needfor most system restores. Thus, the soft delete feature will likely be a welcomeaddition to Exchange implementations.

Systems Administration: Differential Download
Microsoft did not greatly enhance systems administration in Exchange 5.5.Some welcome changes occur with the infamous Directory Service/IS consistencychecker. These changes restrain Exchange's ability to rehome public foldersafter you remove a directory replication connector. (Those who have beenafflicted by this problem will know what I mean). Overall, you have much morecontrol over homing public folders. For example, you can now move a publicfolder's home from site to site in a single step.

Save Window Contents is a hidden feature. Have you ever wanted to capturedetails of the information reported by the administration program, perhaps forlater analysis? Well now you can. First, you populate the right-hand window,perhaps with information about the amount of space each mailbox uses. Then, youclick on File.Save Window Contents to write the data out to a Comma SeparatedValues (CSV) file. This file is a great example of a feature slipped into theproduct by an engineer who thought it would be useful. In this case, it is!

My favorite new feature is differential download of the offline address book (OAB). I travel a lot and depend on the OAB when I'm disconnected from the network. I download the OAB often because I need accurate information. In the past, downloading this 55,000-user OAB took many minutes. But with differential download, I now receive only the changes that have occurred since my last download. My telephone bills are much lower!

Interconnectivity: New Connectors
Exchange has always offered a strong lineup of connectors. Microsoft'sbuyout of LinkAge Software in May further strengthened the lineup because thebuyout led to the addition of Lotus Notes, IBM PROFS, and IBM SNADS connectorsin Exchange 5.5.

The new connectors will likely satisfy your messaging and communicationneeds. Interoperability with Lotus Notes is good. You can send rich-text formatmessages, documents, and other attachments between the two systems without fuss.You can also receive delivery receipts and other status-type messages. Directorysynchronization between Exchange and Lotus Notes is relatively straightforwardand works much like the synchronization between Exchange and Lotus cc:Mail.

Although the Lotus Notes connector's messaging and communication functionsare strong, some restrictions exist. For example, you cannot encrypt messages ineither direction and you cannot synchronize Exchange public folders and LotusNotes databases. (Microsoft will likely close these relatively minor gaps overtime.)

You need to install some of the dynamic link libraries (DLLs) that LotusNotes provides on the server to configure the Lotus Notes connector. But asidefrom the DLL installation, you can use Exchange 5.5's administration program tomanage the connection.

Because Lotus Notes enjoys a high profile in the market, the Lotus Notesconnector will likely receive most coverage. However, the PROFS and SNADSconnectors are important, too, because they will ease the introduction ofExchange into corporate environments that use PROFS and SNADS email systems.Although PROFS and SNADS email systems are not at the cutting edge, they offerdependable service (albeit at a much-reduced level of functionality compared toExchange).

The SNADS connector requires Microsoft SNA Server (2.11 or 3.0) and handlesthe popular SNADS messaging systems, such as Fischer TAO, Soft-Switch Centraland Lotus Message Switch, and Software AG CONNECT. Directory synchronization is unavailable for PROFS and SNADS connectors in Exchange 5.5, but Iwouldn't be surprised if this feature appeared in the future. PROFS calendaringis also unavailable.

Exchange 5.5 is not ignoring older connectors, either. Spamming and othernefarious acts are a fact of Internet life. You can prevent such acts with theExchange Internet Mail Service, which lets you control incoming Simple MailTransfer Protocol (SMTP) connections. For example, you can insist onauthenticated incoming SMTP connections for the Internet Mail Service,effectively stopping spammers from sending your users unwanted messages. Screen3 shows how to set an authenticated connection as properties of the InternetMail Service.

Exchange 5.5 offers unrivalled connectivity to other messaging systems. Thecombination of a heavy-duty MTA and a wide set of connectors deliversfunctionality that major competitors can't match. For example, Exchange 5.5'sMTA can increase its capacity to process messages by splitting a single MAPIqueue into seven. Splitting queues lets servers process a much greater quantityof mail.

The Lotus Notes connector is available in both editions of Exchange 5.5,but you must buy the Enterprise Edition to get the PROFS or SNADS connectors.(For information about which Exchange edition to use, see the sidebar "TwoEditions Are Available," page 170.) The new connectors are available foronly Intel systems, but Microsoft promises to release Alpha versions soon,probably in a service pack, in early 1998. The connectors are available only inEnglish, so for French, German, or Japanese versions, you'll have to wait forthe service pack.

Clients: Better Support
A 16-bit version of Outlook is available for the first time. In addition, anApple Macintosh version of Outlook is available to complete the Outlook lineupacross client platforms.

Microsoft has upgraded Outlook in many ways. For example, you can nowaccess Schedule+ and Outlook calendars from Web browsers. Outlook also supportsdeleted-items recovery and HTML forms. You can create and save a form in HTMLformat, much like what's possible with Word documents. You can also use a wizardto convert existing forms created with earlier versions of Exchange to HTML.

Secure MIME (S/MIME)-capable clients, such as Outlook Express or NetscapeCommunicator, can send encrypted messages to each other via Exchange 5.5. (Likethe other previous clients, IMAP4 clients still need a client access license.)However, Exchange servers don't encrypt or decrypt messages--those tasks areleft to the client. You can expect to see S/MIME capabilities in a futurerelease of Outlook, but not when Exchange 5.5 ships.

Exchange 5.5 now supports IMAP4, as Screen 4 shows. This addition is partof Microsoft's continuing effort to have Exchange 5.5 support as many clients aspossible.

Enabling Technology: The Exchange Scripting Agent
Exchange 5.5 introduces the Scripting Agent, also known as the EventService, to invoke processing when changes (called events) occur in folders. Ifyou add, change, or delete items in a folder, the Scripting Agent will triggeran application to run. However, you need to create the code that tells theScripting Agent which application to trigger. As a result, the Scripting Agentis a diamond in the rough because it needs application developers to takeadvantage of its capabilities. Even so, the Scripting Agent is already laying afirm foundation for document management and workflow applications in Exchange5.5. A future issue of Windows NT Magazine will supply more informationabout the Scripting Agent.

Chat Service
I'm not quite sure how people will use the new Chat Service. An InternetLocator Server supplements the Chat Service, letting users locate people in theExchange directory and connect to them for an online discussion. Supposedly, youcan combine the Chat Service with Microsoft NetMeeting to incorporate onlinecommunication into active pages so that companies and their customers can haverealtime chats. I'm a little skeptical about the overall usefulness of thesefeatures, but I'm happy to wait and see.

Exchange's Journey Is Not Over
Keeping up with Exchange's rapid pace of development can be exhausting attimes. Exchange 5.5, with its many new developments, is no exception. Exchange5.5 now supports all the major Internet protocols, helping it to achieve clientuniversality. You can reasonably argue that Exchange 5.5 is at least as pure anInternet citizen as any of its competitors. In addition, you can use Exchange5.5's massive information store, two-node cluster support, and deleted-itemsrecovery to build large, cost-effective servers.

But Microsoft will face several challenges in 1998. The next version ofExchange will need to support NT 5.0, which will involve a move toward a unifieddirectory based on the Active Directory. At the same, Exchange will need tosupport true clustering in MSCS Phase 2 and take advantage of new hardwaredevelopments in disk, tape, and CPU. Most important, Microsoft will need toaddress manageability. Exchange 5.5 provides many administration features andtools for small to midsize deployments but provides relatively few for largeimplementations. Given the drive and pace behind Exchange, I'll be interested tolearn how Microsoft engineers meet these challenges.