Exchange Server 5.5 Administration
Hierarchy
| Organization |
| Site | Site | Site |
| Server(s) | Server(s) | Server(s) |
The organization is the highest level in the Exchange hierarchy. There is generally only one Organization. The sites fall under the organization and are helpful to separate into geographical areas. There can be one or more servers in a site that do the actual handling of messages, public folders and information for the site.
Components
Core components
Directory Service(DS)
– Holds organizational information including users, servers and distribution lists. Maintains directory information for the organization and automatically replicates to all severs in a site. Holds the Global Address List(GAL)Message Transfer Agent(MTA) – routes messages between servers and sites. Talks to MTA’s from other Exchange servers, X.400 mail systems MTA’s, or Microsoft mail connectors conforms to X.400 standards.
Information Store(IS) – Databases of public folders and user messages. Consists of public and private information store.
Public Information Store – Maintains information placed in public folders to be shared among users.
Private Information Store – Maintains messages sent to one person or a group in private folders. E-mail in private folders is available only to persons with permissions to the mailbox associated with the private folders.
System Attendant (SA) – Maintains routing tables and provides diagnostics and logging for connectors.
First service to start. Generates E-mail addressees for new clients as they are created in the directory. Reclaims space used by deleted objects. Builds route tables for the site. Maintains message-tracking log.
Additional Components
Internet Mail Service
– Allows Exchange to talk to SMTP-based mail systemsInternet News Service – Allows USENET newsgroups to be accessed as public folders and public folders to be accessed as USENET newsgroups
Outlook Web Access – Allows for web-based E-mail, Address Book and public folder access
Microsoft Mail Connector – Allows Exchange to talk to Microsoft Mail 3.x systems
Directory Synchronization – Synchronizes directories between Exchange and Microsoft Mail 3.x systems
Microsoft Schedule+ Free/Busy Connector – Allows sharing of free and busy time info between Outlook calendar and Schedule plus versions 7.0 and 1.0
Connector for cc:Mail – Allows exchange to transfer messages and synch directories with Lotus cc:Mail.
Connector for Lotus Notes - Allows exchange to transfer messages and synch directories with Lotus Notes.
PROFS – Provides connection between Exchange and IBM OfficeVision/VM
SNADS – Provides connection between Exchange and SNADS compliant systems such as: IBM OfficeVision/VM, IBM OfficeVision/400, Verimation MEMO, and Soft
Switch Central and LMS.
Key Management Server – Provides encryption and digital signatures.
Clients Supported
POP3
– Outlook Express, Microsoft Internet Mail, Netscape Navigator, and EudoraIMAP4 – Outlook Express and Netscape Navigator
HTTP – Internet Explorer 3.0x and 4.0, Netscape Navigator and Netscape Communicator.
How Exchange handles data
DatabasesExchange has two databases, one for the Private information store (mailboxes) and one for the Public information store (public folders). These files are priv.edb and pub.edb and are located in the exchsrvr\mdbdata directory.
Log Files
Exchange uses the standard database transaction log method to write data to the database. Data is first written to log files, then in times of low CPU activity data is written to the database. The transactions in the logs are marked as committed once they are written to the database. Having these transactions in the database as well as in the logs provides a form of redundancy in the event of a database failure. The log files are always 5 MB. When a log file reaches 5MB, a new log is started. The log files are numbered sequentially starting with edb00001, edb0002, etc. For optimum recoverability the log files should be kept on a separate physical disk from the databases.
Exchange keeps track of these transactions in the log files by using a file called edb.chk. The edb.chk file keeps track of all transactions that have occurred. Once all transactions within a log file are written to the database, the edb.chk file marks the log OK to purge. Log files are only purged after a full backup is run!! Having all of these log files will allow you to restore the Exchange database in the event of a disaster and Exchange will replay all of the log files when it is started. This will allow and up to the minute disaster recovery.
Reserve Logs
Exchange creates two 5MB logs and calls them res1.log and res2.log. These are used if Exchange runs out of space to create new log files. Exchange will write any transactions to these reserve logs and shut down the services. At this point you will have to run a full backup to clear the logs. This is why it is so important to monitor your Exchange backups and also your disk space on your Exchange servers
Backups
The exchange databases are not available to be backed up when the Exchange services are running as Exchange locks the databases for exclusive use. The way Exchange works around this is to use an Exchange aware backup solution. Exchange ships with an updated version of NTbackup that can accomplish this plus most third party backup solutions are Exchange aware. While Exchange is being backed up, it deals with transactions a little differently. If a transaction effects a portion of the database that has not been backed up yet, Exchange writes the information to the database. If a transaction effects a portion of the database that has already been backed up, Exchange writes the transaction to a temporary or patch file to be written after the backup. These patch files are also backed up so Exchange can replay them and commit them to the database in the event of disaster recovery.
Circular Logging
By default, Exchange uses circular logging. With circular logging, exchange keeps a few log files and overwrites them as more data comes in instead of keeping all log files until a full backup is run. Exchange will only overwrite the log file if all data has been committed to the database. The problem with this is that if the Information store gets corrupted and you restore it from tape backup, you lose all data since you last ran a backup, as you do not have all of the logs to replay because they have been overwritten. If you are looking for high availability and recoverability of your data, you will want to disable circular logging when you build your Exchange server.
Deleted Item Retention
A new addition that Exchange5.5 brought us was deleted
item retention.
Deleted item retention can be enabled on both the public and private
information store. When deleted item retention is enabled, all items
deleted through a mail client are moved to a hidden folder. Only
after the time period specified for deleted item retention has expired will
the mail actually be deleted. You have the option to not delete these
items until a full backup is run even after the deleted item retention time
has expired. Items in the deleted item retention hidden folders do not count as part
of a users mailbox size limit as they are flagged as deleted. This
should be considered when you plan for storage requirements. Deleted items can be recovered through the mail client.
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