Why a transaction log backup might contain two Snapshot copies

When you use SnapManager with Exchange Server 2003 in a Windows Server 2003 environment, a single backup creates two Snapshot copies instead of one if the SnapInfo directory is configured on the same volume as the transaction log.

The following Snapshot copies are created:

A VSS Snapshot copy in the transaction log
The exchsnap__* Snapshot copy is created at the same time as the corresponding database Snapshot copy of the same name.
The SnapInfo backup Snapshot copy for protecting the SnapInfo directory
The eloginfo__* Snapshot copy is created at the end of the backup operation. It is used for transaction log verification and for backup protection. If the backup set is archived, the eloginfo__* Snapshot copy, along with the Exchange Snapshot copy, can be used for a SnapManager restore operation.
Note: For VSS backups, the transaction log LUN Snapshot copy is used instead of the SnapInfo directory LUN Snapshot copy to verify the integrity of the transaction logs during remote database verification.

When SnapManager uses VSS to back up and restore data, the SnapInfo directory and transaction log are on the same volume.

Suppose the SnapInfo directory is on the same LUN as the transaction log in an Exchange Server 2003 environment with Windows Server 2003. The console output shows that the transaction log volume contains Snapshot copies with the same name as that of the Exchange database Snapshot copy.

Volume netappnj1_logs
working...
date name
____________ ________
Jan 30 01:04 eloginfo__mailnj1__recent
Jan 30 01:00 exchsnap__mailnj1__recent
Jan 29 13:03 eloginfo__mailnj1_08-29-2006_13.00.00__daily
Jan 29 13:00 exchsnap__mailnj1_08-29-2006_13.00.00__daily
Jan 29 01:04 eloginfo__mailnj1_08-29-2006_01.00.00
Jan 29 01:00 exchsnap__mailnj1_08-29-2006_01.00.00
Jan 28 13:03 eloginfo__mailnj1_08-28-2006_13.00.00__daily
Jan 28 13:00 exchsnap__mailnj1_08-28-2006_13.00.00__daily
Jan 28 01:04 eloginfo__mailnj1_08-28-2006_01.00.00
Jan 28 01:00 exchsnap__mailnj1_08-28-2006_01.00.00
Jan 27 15:36 eloginfo__mailnj1_08-27-2006_15.30.15
Jan 27 15:30 exchsnap__mailnj1_08-27-2006_15.30.15
Jan 20 15:35 eloginfo__mailnj1_08-20-2006_15.27.35
Jan 20 15:27 exchsnap__mailnj1_08-20-2006_15.27.35

If you are not aware of the configuration details, you might expect to see only the eloginfo__ Snapshot copies and not the exchsnap__ Snapshot copies.

Note: Volume size is unchanged, because the backup set still captures the same total number of changed blocks on the storage system, even though two Snapshot copies are used instead of one.