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Are you looking for a performance increase to Online Storage for Backup Exec?

Level 4
Employee Accredited Certified

There are two configuration changes you can make that will enhance the performance of file uploads for Online Storage for Backup Exec.


1) Deselecting “verify after” and
2) modifying the upload chunk size.



Deselecting “Verify after job completes” significantly improves the performance of file uploads.


Steps for changing the setting in Backup Exec.

  1. Go to the properties of the Backup Exec duplicate job
    a. This can also be done while you’re creating the job.
  2. From the left hand pane under Settings, select “Advanced”.
  3. In the right hand pane, ensure checkbox next to "Verify after job completes” is UNCHECKED.
  4. Click Submit.

Why not verify for the duplicate job?

The purpose of “Verify” in Backup Exec is to confirm the ability to restore data from generally unreliable tape media. Since Online Storage for Backup Exec is using high end disk based online storage as the backup target, the additional time required to “Verify” (i.e., resend data back to the BE server for verification) is not warranted. The Online Storage agent already verifies the data backed up to ensure a successful file transfer.



The Online Storage agent is configured with a static data unit “chunk” size that is not optimal for all network configurations. You can tune the upload chunk size to maximize throughput through registry key setting for Backup Exec.


Steps for adding the registry key

  1. Visit and perform a speed test.
  2. Record the value displayed for the upload speed transfer rate.
  3. Use this value to look up recommended chunk size in table below.
  4. Create the registry key under 
    • DWORD Value
    • Name: Cache Mbytes
    • Base: Decimal
    • Possible values: [2, 4, 8, 16, 32]
  5. Restart Backup Exec Device & Media Server Services



1) Setting the Cache Mbytes value higher than recommended can actually reduce performance and waste network bandwidth. Setting values other than 2, 4, 8, 16, or 32 will be ignored as invalid.

2) Default Value is 2 Mbyte cache.


A future software update will calculate the optimum value and dynamically adjust the “chunk” size for the best performance.


Of the two configuration changes, Deselecting Verify should have the most impact on improving performance.

At Symantec Protection Network, we strive to provide the highest quality online service experience.

If you need assistance making this change or have any questions about the service, please contact the 24/7 Symantec Protection Network support team. Our toll-free number is 866-223-5977, or you may contact us via email at:


We sincerely thank you for using Symantec Protection Network as we strive to make our services exceed your business needs.

Message Edited by Ted_Migdal on 12-19-2008 02:20 PM
Message Edited by Ted_Migdal on 01-06-2009 09:15 AM
Message Edited by Ted_Migdal on 01-06-2009 10:04 AM

Level 2
Partner Accredited

This is not just a performance issue - in my case having the "verify" enabled makes the job fail outright after getting to approx. 99% (I tried it a couple of times).  I called tech support and was told the failure was a known issue.

Level 4
Employee Accredited Certified

Does this happen to you with every backup job? How big is the backup job that fails at 99%?


Level 2
Partner Accredited

Sorry for the delay.  The job wasn't terribly large - about 3.2 GB.  The 99%-to-failure happened every time I tried to backup with "verify" enabled.


When I disabled the Verify, the job took the same amount of time, but it actually completed successfully.

Message Edited by mabman on 11-24-2008 02:30 PM