Normal (full) and copy backups |
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By Jerry Cochran
01 Nov 2004 | SearchExchange.com |
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The following is tip #2 from "20 tips on protecting and recovering Exchange data in 20
minutes," excerpted from the book, "Mission Critical Microsoft Exchange 2003" (Digital
Press, a division of Elsevier, Copyright 2004). For more information about this book and
other computing titles, please click here.
Return to the main page for
more tips on this topic.
The normal backup (also referred to as a full backup) is the fundamental unit of operation
for most Exchange deployments. Regardless of the strategy you select for backup, the normal
backup type will be part of your operational procedures. With a normal backup, both the
database files and the log files are copied to tape. In addition, the log files are truncated
or deleted once they have been copied to the backup media.
The truncation point for the transaction log files is the current database checkpoint
location. The normal backup operation is also important to database integrity since only
during a normal backup are the 4-KB database pages checked for corruption (they are also
checked during copy backups and on-line database maintenance as well). This is accomplished
by verifying each page read to make sure that the page number requested is the page the
database engine received. Next, each page's CRC information (contained in the page header)
is verified to ensure that the data contained in the page is valid. The normal backup is also
important to the ESE Page Zeroing feature, which I will discuss later in this chapter. To
restore from a normal backup, you only need to restore the complete set and allow the ESE
database engine to replay any log files required for the database to be in a consistent
state.
Similar to the normal backup is the copy backup. A copy backup differs in that it does not
truncate or purge log files once they have been copied to tape. In addition, the copy backup
does not update database backup context information contained in the database file header.
Copy backups are very useful for archival purposes or other scenarios in which you want to
back up your Exchange databases, but do not want to disrupt the normal backup schedule. A
copy backup performs the same functions of integrity checking and page-zeroing (if enabled)
as the normal backup.
Get more "20 tips on protecting and recovering Exchange data in 20 minutes". Return
to the main
page.
About the author: Jerry Cochran is a contributing editor for Windows IT
Pro and Exchange & Outlook Administrator and a group program manager for
Microsoft. He is the author of Mission-Critical Microsoft Exchange 2000 (Digital
Press).
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