How to run dcscan to validate a Backup Exec Deduplication Storage Folder or a specific container within the folder.

How to run dcscan to validate a Backup Exec Deduplication Storage Folder or a specific container within the folder.

Article: 100006521
Last Published: 2021-02-16
Ratings: 3 2
Product(s): Backup Exec

Problem

Need to verify that the Deduplication Storage Folder is not corrupted.

If a container file (.bin) is suspected of being corrupted, or if it is necessary to find out which of two files is the best one to keep, the dcscan program can be used to check the contents of the .bin files in question.

 

Cause

If a container file (.bin) is suspected of being corrupted, or if it is necessary to find out which of two files is the best one to keep, the dcscan program can be used to check the contents of the .bin files in question.

Solution

The dcscan.exe program can be used to validate the contents of a Deduplication Storage Folder as a whole, or just to validate a particular container.  Please note that a rough estimate on the amount of time it takes to run dcscan is one hour per terabyte of data.  This time will also be affected by the speed of the system and the speed of the disk subsystem.  So, on a 24 terabyte deduplication folder, this could easily take 24 hours to run.

The dcscan.exe program can run while the Deduplication Storage Folder is online and being used, but it will have a performance impact.  It is also necessary to temporarily turn off compaction on the Deduplication Storage Folder to prevent false errors from being reported.  It is important to remember to turn compaction back on as described below.

When the Deduplication Storage Folder is online (Backup Exec Deduplication Manager / Engine services started)

1. Disable Lockdown settings.

To disable the Lockdown, click Backup Exec Settings > Network and Security > Disk storage lockdown settings > Disable and enter the System Logon Account credentials.

NOTE: Lockdown setting should be enabled back after running the dcscan

2. Open Command Prompt ( Run as Administrator ) and run the below command -

cd "\Program Files\veritas\Backup Exec"

crcontrol --compactoff      (Note: two dashes before compactoff)

dcscan --verify -q -H -a > crcerrors.txt 2>&1       (Note: two dashes before verify)

crcontrol --compacton       (Note: two dashes before compacton)

If the crcerrors.txt file is zero bytes, then the dcscan program did not find any corruption inside the deduplication folder.

IF DEDUPLICATION ENGINE SERVICE IS NOT RUNNING - 

The dcscan.exe program requires access to the deduplication database in order to perform its function.  If dcscan.exe is run without Deduplication Engine Service running it throws the below error : 

C:\Program Files\veritas\Backup Exec>dcscan --verify 65
Error: 67: Database: connection to database crdb at localhost:10085 failed (could not connect to server: Connection refused (0x0000274D/10061)
        Is the server running on host "localhost" and accepting
        TCP/IP connections on port 10085?
)
Error: 53: Database Manager: could not access storage database (connection actively refused).
Error: 4: Failed to run database class
Error: 4: Failed to read startup mode

Ensure the dcscan command is run with the deduplication services running.

From a command line window:
cd "\Program Files\veritas\Backup Exec"
dcscan --verify -q -H -a > crcerrors.txt 2>&1       (Note: two dashes before verify)

If the crcerrors.txt file is zero bytes, then the dcscan program did not find any corruption inside the deduplication folder.

 
Validating a specific container file

If it is only necessary to check a specific container file, that can be done by using the following command line in place of the dcscan command lines above:

dcscan --verify 65 -q -H -a > crcerrors.txt 2>&1 

Where 65 is the number of the container to be validated.  The containers are in the data directory of the storage folder.  Do not erase or move any of the files in the data directory.

What to do if data corruption is found

If data corruption is found in the deduplication folder, it can only be addressed using a tool available to Veritas Technical Support.  Please make sure to keep the associated crcerrors.txt file.  Having it available will shorten the time necessary to address the issue.

 

Applies To

Backup Exec media server with the Deduplication Option and a Deduplication Storage Folder.

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