Document ID: 284159
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Synthetic full backups show an unexplained lower byte-count than baseline and/or last synthetic full and first incremental in a synthetic policy backup shows a higher byte-count than usual in Backup Exec 10.0 and 10d for Windows Servers
Details:

The synthetic backup issue described in this article is only encountered when the following conditions are met:



The synthetic backup issue occurs due to an incorrect sorting process that is encountered by Backup Exec if there were directory changes made after the initial synthetic baseline backup was performed. As a result of this sorting error, Backup Exec may fail to process all directories after new subdirectories are added to a system. The result is an observably smaller backup than would be expected.

Note: The size discrepancy will depend on where in the folder structure a folder was added or deleted.


In the below example, Figure 1 shows a portion of the directory structure as it existed before the synthetic baseline backup. Figure 2 shows the nested "e" folder added just before the synthetic incremental job was run.


Figure 1 and Figure 2
 

When the incremental backup is run and the new "e" folder is encountered, all data within the "b" directory and in the remainder of the "test" folder is incorrectly backed up due to the incorrect sorting process mentioned above.

Permanent Fix:

This issue has been resolved in the following Backup Exec Hotfixes:

Note: Backup Exec 10.0 5484 installations will need to be upgraded to one of the versions listed below.

Hot Fix 31 for Backup Exec 10.0.5520 SP2
 http://support.veritas.com/docs/284167
Hot Fix 33 for Backup Exec 10.1.5629 (10d) SP1
 http://support.veritas.com/docs/284165


Post Hotfix Instructions:

1. After the appropriate hotfix has been installed, a new baseline or priming Synthetic Backup should be performed at the earliest convenience.

2. If a selection script has been created by hand, and directories were entered in a different case than what exists on the system (eg. c:\MYDIR instead of c:\mydir), the same directory will be backed up twice under both of these names. This applies to Windows systems only, as UNIX systems are case sensitive.


Workaround:

Symantec strongly recommends that all customers performing synthetic backups perform full backups until the hotfix for the installed version of Backup Exec has been applied.


Products Applied:
 Backup Exec for Windows Servers 10.0, 10.0 5484, 10.0 5484 SP1, 10.0 5484 SP2, 10.0 5484 SP3, 10.0 5484 SP4, 10.0 5520, 10.0 5520 SP1, 10.0 5520 SP2, 10d (10.1) 5629
Last Updated: July 13 2006 02:00 PM GMT
Expires on: 365 days from publish date
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Subjects:
 Backup Exec for Windows Servers
   Application: Backup
   Application Basics: Backup-Restore
   Publishing Status: Techalert

Languages:
 English (US)

Operating Systems:
Windows 2000

Advanced Server, Server

Windows Server 2003

Enterprise Server, Standard Server