Understanding SnapManager Backup

What SnapManager Backup does

SnapManager Backup performs a full online backup of the Exchange storage groups' databases and transaction logs. SnapManager Backup uses snapshot functionality to create real-time, online, read-only copies of Exchange databases. After the selected storage groups (Stores) are safely backed up, the transaction logs that are already committed to the databases captured in the backup are deleted.

Tasks a SnapManager backup performs

The following tables outline the steps SnapManager Backup takes when creating a backup, for Windows 2000 Server and Windows Server 2003.

Note
The following tasks are performed in their entirety for each volume containing the storage groups to be backed up. If two separate volumes are involved, the task list is performed once for the first volume, then again for the second volume.

SnapManager Backup tasks for Windows 2000 Server

Task	Process
1	Check SnapManager license.
2	Rename most recent SnapInfo directory, if required.
3	Rename most recent snapshot, if required.
4	Create SnapInfo directory for this backup.
5	Initiate online backup.
6	Back up database files.
7	Create database snapshot.
8	Back up transaction logs.
9	Truncate transaction logs.
10	Create SnapInfo snapshot.
11	Delete SnapInfo snapshots for the deleted backups.
12	Delete any specified older backups.

SnapManager Backup tasks for Windows Server 2003

Task	Process
1	Check SnapManager license.
2	Rename most recent SnapInfo directory, if required.
3	Rename most recent snapshot, if required.
4	Create SnapInfo directory for this backup.
5	Initiate VSS backup.
6	Gather Exchange metadata and start VSS snapshot set.
7	Add all required volumes to VSS snapshot set.
8	Create volume shadow copy. (The transaction logs are backed up and truncated during this step).
9	Create SnapInfo snapshot.
10	Delete SnapInfo snapshots for the deleted backups.
11	Delete any specified older backups.

What the SnapManager backup set is

A SnapManager backup set, sometimes called just the "backup set", consists of all data that you would need to be able to perform a restore, regardless of whether this data exists on the same LUNs or volumes. The backup set contains the following items:

Exchange databases
Exchange transaction logs
SnapInfo directory

What storage group sets are

Exchange storage groups (Stores) stored on a single volume that belong to the same Exchange server are referred to collectively as a storage group set. When you select an Exchange storage group for backup, all storage groups composing its storage group set are automatically selected for backup.

SnapManager Backup backs up the complete set of storage groups--all of which constitute the storage group set--in parallel. (Thus, these storage groups share the same backup name and date-time stamp.)

Note
Even though the backup includes all storage groups in the storage group set, you can still restore the storage groups individually.

How partial backups work

If the backup of some of the storage groups or databases in the storage group set fails, those in the set that were backed up successfully can still be restored. Because each database constitutes its own backup, or file, it is restored discretely, independent of backups of the others in its storage group set, even though the backup of all databases and storage groups in the set was synchronized.

Volume-wide backup

When a snapshot is taken of a LUN for a SnapManager backup, the entire volume is captured in that snapshot. However, that backup is valid only for that Exchange server. If data from other Exchange servers resides on the same volume, it is not restorable from that snapshot.

Backup of multiple volumes

SnapManager Backup performs backups in parallel on all LUNs that belong to the same Exchange server and share a single filer volume. When a storage group set spans more than one volume, the resulting backup set contains more than one database snapshot but is still restorable as a single entity.

Storage group icons

To help you keep track of which of your storage groups share a volume, the storage group icons on the SnapManager Backup and Verification tab are color-coded by the volume they reside on.

Note
If a storage group spans multiple volumes, its icon contains three colors.

SnapManager Backup and the SnapInfo directory

The SnapInfo directory contains the information about each storage group set created by SnapManager Backup. A subdirectory under the SnapInfo directory is created for each backup set. Each backup SnapInfo subdirectory contains the transaction logs backed up as part of that backup, as well as the recovery information for that specific snapshot.

By default, the SnapInfo directory is on the LUN that stores the Exchange transaction log files, but this is not a requirement. The SnapInfo directory cannot reside on the same LUN that stores the Exchange database files.

Every time a SnapManager backup is created, a new backup set subdirectory is created under the SnapInfo directory and is populated with the appropriate information and data. A complete backup set consists of this SnapInfo subdirectory and the corresponding snapshots of the LUNs that store the Exchange databases and transaction logs.

How backup management groups are used

Backup management groups are used to determine which backups are targeted for automatic deletion and verification. For example, when you run or schedule a backup, you can specify how many of the most recent backups you want to retain. Only backups of the specified backup management group are deleted.

SnapManager provides the following backup management groups:

Standard
Daily
Weekly

Using the Standard backup management group for all backups results in the same behavior as earlier versions of SnapManager for Microsoft Exchange.

Note
The backup management group does not depend on or enforce how often that backup is performed. It only enables you to group your backups for management.

Example

Suppose your company wants to take regular backups between 7:30 a.m. and 7:30 p.m. You want to keep the last backup of the day and keep it around for a few weeks, and you want to keep one backup per week for several months for archiving.

To achieve this using backup management groups, you could use the Standard backup management group for the backups during the day, and use a separate backup job to create one backup in the Daily management group at the end of the day. Then, once a week, you could use another job to create a backup in the Weekly backup management group.

You could then decide how many backups to retain independently for each backup management group. For example, you could keep 10 Standard backups, 7 Daily backups (one week's worth) and 4 Weekly backups (one month's worth).

If your Daily or Weekly backup job failed for any reason, you could promote the most recent successful Standard backup to replace the Daily or Weekly backup by changing its backup management group. For information about how to change a backup's management group, see Changing the backup management group.

Changing the backup management group

To change the backup management group, complete the following steps.

Note
The window shown in this procedure is for the Exchange 2000 or 2003 version of SnapManager. If you are using Exchange 5.5, some of the text you see is slightly different. However, the actions you take to perform these steps are the same.

Step	Action
1	In the SnapManager main window, select the SnapManager Restore tab.
2	Select (left-click) the backup whose management group you want to change.
3	Right-click the backup and select Change Management Group from the pop-up menu. Result The Change Backup Management Group dialog box is displayed.
4	Review the backups listed in the Backups Sharing This Snapshot list. Note The backup management group for all these backups is changed if you complete this operation. This is because they share a common snapshot.
5	In the New Management Group list, select the backup management group you want to change to. Note When you change a backup's backup management group, you also change that backup's name, because the name includes the backup management group.
6	Click OK. Result The backup management group for this backup and all backups listed in the All Backups Sharing This Snapshot list is changed. Note The report for the backup management group change is in the Miscellaneous report directory.