Benefits of Using Storage Groups

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These days, it is not uncommon to find Exchange 5.5 databases that are well over 20 GB in size. The time necessary to back up these databases can exceed several hours. The problem with this is not the time it takes to back up the database, but the time it takes to restore such a large database. During the restoration, of course, your users' productivity goes down the drain. In Exchange database planning, the old cliché is a good one: Always plan for failure so that you can succeed. You'll find that prudent use of storage groups will help you succeed during disaster recovery.

In implementing storage groups and allowing multiple databases per Exchange server, Microsoft has made some tremendous changes to the Extensible Storage Engine (ESE) database architecture. These changes significantly enhance recoverability and minimize unproductivity when an Exchange database becomes corrupted. In addition, storage groups offer several key benefits:

  • Each server can host more users than before.
  • Each database can be backed up and restored individually.
  • Each server can host multiple businesses.
  • A separate store can be used for special mailboxes.
  • Circular logging can apply to individual storage groups.

These points are discussed in the sections that follow.

Increased User Support

Probably the largest benefit of storage groups is that they allow you to spread users across databases and storage groups on the same Exchange 2000 server. This means three things: (1) you can support more users on a single server than was possible in Exchange 5.5, (2) you'll have less downtime when a database becomes corrupted, and (3) you can host more users on an Exchange server because you can keep your databases to a manageable size.

Within a storage group, you can have up to six databases. Each server can house up to four storage groups. Thus, each server can have a maximum of 24 databases.

However, when you run the Information Store Integrity Checker (Isinteg.exe) on a database, you must dismount that database. In addition, Isinteg.exe needs a second database for temporary use. Therefore, if you have six databases operating in a given storage group, you will have to dismount a second database so that Isinteg.exe can run properly. If you limit the number of operating databases to five in a single storage group, then you will always have room to run Isinteg.exe without having to dismount a second store.

Having your users spread out across multiple databases means that only a subset of your users is affected if one of your databases goes off line for some reason. The other users can continue to work because their databases are up and running. A database that is offline is considered to be dismounted. Its icon appears with a red down arrow in the Exchange System snap-in, as shown in Figure 11-1.

click to view at full size.

Figure 11-1. Online databases and an offline database (MBX3) in a storage group.

Individual Backup and Restore

Because each individual database can be mounted or dismounted, you can back up and restore databases individually while other databases in the same storage group are mounted and running. Consider a scenario in which you have created five mailbox stores in the same storage group, one for each of five departments. If one of those stores becomes corrupted, the other four can remain mounted while you restore the fifth store from backup and then mount it again. You are not required to dismount all of the stores in a storage group in order to restore one of them. And if one store becomes corrupted and cannot be mounted, it does not stop other stores in the same storage group from being mounted and available to users.

Hosting of Multiple Businesses

If you manage e-mail for multiple businesses, you can host them on a single server. You can create an individual store for each business or even devote a storage group to a business, if needed. In either case, Exchange 2000 Server keeps the information for each business completely separate in its respective store, unlike Exchange Server 5.5.

Having the stores separate and distinct allows you to set up different administrative schedules for the businesses. For instance, some administrators may want to have full backups performed every day while others may need only weekly full backups. Some may want to have each department hosted in a separate store, while others may be happy to house all of their users in the same store. This flexibility makes it easier to meet your customer's needs.

Support for Special Mailboxes

While it is not widely recommended, you can take a special mailbox or set of mailboxes and create them in their own store. One instance when this might be useful would be for a journalizing recipient that receives copies of all appropriate e-mails in your organization to comply with local laws or industry-specific regulations. Another instance might be for a project team that is working with highly sensitive and mission-critical company information. Their work might warrant the use of a separate store or public folder tree.

Circular Logging for a Single Storage Group

You may need to control the transaction logs for some storage groups because of limited disk space. It could be the case, for example, that information held in one native content file is expendable while information held in a different native content file is not. Because you are limited to recovery at the last full backup when using circular logging, you could place your expendable information (such as a history of companywide memos) in one public folder in one storage group for which you permit circular logging, and you could place your users' e-mails in a different storage group that has circular logging turned off. That way, you'll be able to focus your disaster recovery efforts on the most important information. For a description of how circular logging works, refer to Chapter 2.



Microsoft Exchange 2000 Server Adminstrator's Companion
Microsoft Exchange 2000 Server Adminstrator's Companion
ISBN: N/A
EAN: N/A
Year: 1999
Pages: 193

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