XADM: Online Backup Performance Decreases Over Time (815068)

SYMPTOMS

When you perform an online backup of a Microsoft Exchange 2000 Server, you may notice the time that it takes to backup the database slowly increases over time. The time it takes to complete a backup of comparable size may double from the time it took in the first few weeks of operation.

RESOLUTION

To resolve this issue, click to clear the Zero out deleted database pages check box on the properties of the Storage Group. To do so, follow these steps:

Click Start, point to Programs, point to Microsoft Exchange, and then click System Manager.
In the left pane, double-click Administrative Groups, click your administrative group, and then double-click your server.
Right-click your storage group, and then click Properties.
Click to clear the Zero out deleted database pages check box.
Click OK.
Restart the Information Store service so that the change will take effect.

MORE INFORMATION

The Zero out deleted database pages option is designed to overwrite unused pages in the Exchange 2000 Server databases with zeros so that the data in these unused pages cannot be recovered by using conventional means.

When an item is deleted from the Exchange Server, such as when a user deletes a message from their mailbox, the item is no longer referenced and the pages that the item was occupying are marked as unused. With Zero out deleted database pages selected, the data contained in unused pages is overwritten with various characters (either 'z', 'd', 'l', or 'u', depending on the type of page being overwritten) during an online backup. As each database page is written to the tape, the page is then overwritten with zeros in the database on the hard disk. After the backup is complete, the deleted data is on the tape but is no longer in the database and cannot be recovered by using conventional means.