Exchange and Outlook UPDATE, Exchange 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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May 31, 2002—In this issue:
- In Depth: Exchange's ESE Restore Operation
2. NEWS AND VIEWS
- Microsoft Patches Exchange 2000 Server Hole
- Struggling with IIS and Web Administration Issues?
- Raising Windows 2000 Availability—Free Webinar
4. HOT RELEASES (ADVERTISEMENTS)
- Marathon Technologies
- Exchange XADM: How to View the Contents of the Restore.env File
- Featured Thread: Internal Mail Flow Problem
- Results of Previous Instant Poll: Do You Use Exchange Recovery Servers?
- New Instant Poll: If you use Exchange 2000 Server, have you installed Service Pack 2 (SP2)?
6. NEW AND IMPROVED
- eIQnetworks Announces MailAnalyzer
7. CONTACT US
- See this section for a list of ways to contact us.
(contributed by Jerry Cochran, News Editor, [email protected])
In last week's commentary, ("The ESE Backup Process: An Inside Look," http://www.exchangeadmin.com, InstantDoc ID 25350), I dove into the deep waters of Exchange Server's backup operations. Understanding that process can help you better plan and execute disaster recovery for your Exchange deployments. This week, I want to examine the rest of the story: how the Exchange database engine—the Extensible Storage Engine (ESE)—recovers Exchange databases. Armed with this information and last week's discussion of backup operations, you'll be well prepared to tackle the challenges of Exchange disaster recovery.
First Things First
Obviously, a restore operation is an administrator-initiated activity. Before the backup application can restore a database, you must perform two important tasks. First, you need to use the Microsoft Management Console (MMC) Exchange System Manager (ESM) snap-in or some other means (e.g., a script that uses Windows Management Instrumentation—WMI) to dismount the database. Second, you need to use the snap-in or other method to configure the database so that the restore operation can overwrite it. (By default, the database can't be overwritten.) After you've completed these preparatory tasks, the database is ready to be recovered.
Beginning the Restore and Copying the Databases
First, the backup application reads the beginning of the backup set to get a list of available databases. After you select the database to recover, the backup application calls two ESE backup APIs to start the restore. The application asks you for input such as the server to restore to, the location on the server, and a temporary directory for the log, patch, and restore.env files. The application calls the HrESERestoreOpen API to provide this information to ESE, then calls the HrESERestoreAddDatabase API once for each database to be restored. ESE leaves it to the backup application to restore the needed database files to the proper locations. ESE lets the backup application make Win32 file-system calls directly to the OS and lets the backup application copy the database files to disk from the backup set. The reason for ESE's lack of involvement is that it already performed a checksum of the database files during backup, and if the backup set is complete, the databases should be intact. Because the databases being restored are dismounted, letting the backup application copy these files directly to disk is much simpler and faster.
Restoring the Log and Patch Files
Again, the backup application doesn't need ESE's help for a while. The application simply calls the HrESERestoreOpenFile API for each log or patch file to be restored, then copies these files to the temporary directory that the backup administrator specified at the beginning of the backup process. (As I mentioned last week, Exchange 2000 Server Service Pack 2—SP2—and later don't use patch files.) The backup application copies the log and patch files to this temporary directory because these files must remain separate from the log files in the production log-file directory. If naming conflicts or overlaps in the logs on the backup set cause a conflict with the logs on disk, the best course is to copy the log files from the backup set to the temporary directory.
The Restore Environment
After recovering all log and patch files from the backup set, the backup application makes a call that's new in Exchange 2000. Earlier versions of Exchange create the Restore_In_Progress registry subkey during a recovery operation. This key contains information about the recovery operation in progress for the database engine (of which there is only once instance in Exchange Server 5.5 and earlier versions). In Exchange 2000, however, multiple instances of the database engine (i.e., storage groups—SGs) and concurrent recovery capabilities exist, so one registry subkey won't suffice. This change led to the advent of the restore.env file (which stands for Restore Environment). The backup application calls the HrESERestoreSaveEnvironment API during recovery, ESE returns information similar to the information stored in the Restore_In_Progress subkey used in earlier versions of Exchange, and the application saves the information in restore.env in the temporary directory with the log and patch files. (You can use the Eseutil program with the /cm switch to view the contents of restore.env. For more information, see this week's featured Exchange XADM: How to View the Contents of the Restore.env File.)
Completing the Restore and Running Hard Recovery
After the backup application copies all the necessary backup sets for the current recovery operation, the application is ready to complete and terminate its activities and give control back to the Store process (store.exe). The backup application calls the HrESERestoreComplete and HrESERestoreClose APIs to signal ESE that it should take over. At this point, you'd think that the SG that owns the database being recovered would take over and complete the recovery operation. Instead, the Store process instantiates another ESE SG to perform the hard-recovery operation. Hard recovery is the process of applying patch files to the database, replaying log files from the backup set in the temporary directory, and replaying log files from the production log-file directory. After hard recovery is completed successfully, the database is ready to be mounted and made available to users. (Note that you can use Eseutil with the /cc switch to perform hard recovery manually if you're performing simultaneous restores or if hard recovery wasn't completed automatically for some reason.) The recovery SG instance deletes the files in the temporary directory, then is terminated, turning control over to the SG that owns the database.
Too often, Exchange administrators trivialize disaster-recovery operations. However, understanding exactly how backup and restore operations work and how they affect your ability to meet service level agreements (SLAs) for your Exchange deployments is of paramount importance. I hope that this two-part, in-depth look into the internals of Exchange's ESE and its performance of these operations will help you provide the highest levels of availability for Exchange.
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2. NEWS AND VIEWS
(contributed by Paul Thurrott, [email protected])
Microsoft has released a patch to fix an Exchange 2000 Server flaw that can result in Denial of Service (DOS) attacks. For more information, go to the following URLs:
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How can you reduce (or eliminate) data loss and downtime in the event of a site-wide disaster? Attend the latest free webinar from Windows & .NET Magazine and get the answers including what kind of fault-tolerant disk setup to use, what clustering is (and isn't) good at, and best practices for boosting SQL Server and Exchange 2000 Server availability. Register (for FREE) today!
4. HOT RELEASES (ADVERTISEMENTS)
Is Your E-mail System a Legal Liability?
New laws make dropped e-mail messages a potentially serious legal risk. To learn more, get a free copy of "Legal Implications of E-mail Server Downtime."
Each week, Microsoft posts several Exchange Server how-to articles to its Knowledge Base. This week, learn how to dump and view the restore.env file's contents.
Patrick has two Exchange 2000 Server Service Pack 2 (SP2) systems—server1 and server2. He's having trouble with mail flow from server1 to server2 but not in the opposite direction or from external sources. To offer your advice or join the discussion, go to the following URL:
The voting has closed in Windows 2000 Magazine's Exchange & Outlook Administrator Channel nonscientific Instant Poll for the question "Do you use Exchange recovery servers?" Here are the results (+/-2 percent) from the 709 votes:
- 32% Yes, for Exchange 5.5
- 15% Yes, for Exchange 2000
- 17% Not yet, but we plan to do so within the next 12 months
- 36% No, and we have no plans to do so
The next Instant Poll question is "If you run Exchange 2000 Server, have you installed Service Pack 2 (SP2)?" Go to the Exchange & Outlook Administrator Channel home page and submit your vote for a) Yes, b) Not yet, but we plan to do so within the next 6 months, or c) We don't run Exchange 2000.
6. NEW AND IMPROVED
(contributed by Bob Kretschman, [email protected])
eIQnetworks announced MailAnalyzer. This software provides data about message traffic on an Exchange Server system, the use of messaging resources, cost of ownership, and peak traffic hours. Messaging administrators can also monitor email for offensive content. MailAnalyzer provides report customization, creation, management, and online Help wizards. The product uses information gathered from the Exchange message-tracking logs, the Exchange Directory, Windows 2000 Active Directory (AD), and Windows NT event logs. MailAnalyzer runs on Exchange 2000 Server and Exchange Server 5.5 systems. The product costs $399; a free trial download is available. For more information, contact [email protected]
7. CONTACT US
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