Problem
When using NBD/NBDSSL transport mode with Backup Exec 21.4 and later, see the following article for information about tuning backup performance.
About VMware Asynchronous read operations during backup
Hotfix 176937 for Backup Exec 2010 R3 improved the performance of VMWare related backup or restore jobs and the same is included in the later versions. The best improvement gain is usually seen with backups using SAN transport type over backups using NBD backup type. It will be a better impact with NBD type backup if the network is 10GB end to end. With this improvement there are 8 registry keys that can be modified towards getting optimal performance.
Registry Keys and Location:
Before BE 21 - HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Backup Exec For Windows\Backup Exec\Engine\VMware Agent
BE 21 onwards - HKEY_LOCAL_MACHINE\SOFTWARE\Veritas\Backup Exec For Windows\Backup Exec\Engine\VMware Agent
Warning: Incorrect use of the Windows registry editor may prevent the operating system from functioning properly. Great care should be taken when making changes to a Windows registry. Registry modifications should only be carried-out by persons experienced in the use of the registry editor application. It is recommended that a complete backup of the registry is done prior to making any registry changes.
Values Default
Hex (dec)
"Enable Buffered Reads" =dword:00000001 (1)
"Number of Read Buffers" =dword:00000004 (4)
"Size of Read Buffers" =dword:00000400 (1024)
"Enable Buffered Writes" =dword:00000001 (1)
"Number of Write Buffers" =dword:00000004 (4)
"Size of Write Buffers" =dword:00000400 (1024)
"Write Thread Priority" =dword:00000000 (0)
"Read Thread Priority" =dword:00000000 (0)
Values Recommended - 1GB NBD
Hex (Dec)
"Enable Buffered Reads" =dword:00000001 (1)
"Number of Read Buffers" =dword:0000000a (10)
"Size of Read Buffers" =dword:00001000 (4096)
"Enable Buffered Writes" =dword:00000001 (1)
"Number of Write Buffers" =dword:0000000a (10)
"Size of Write Buffers" =dword:00001000 (4096)
"Write Thread Priority" =dword:00000001 (1)
"Read Thread Priority" =dword:00000001 (1)
Values Recommended - SAN/10GB NBD
Hex (Dec)
"Enable Buffered Reads" =dword:00000001 (1)
"Number of Read Buffers" =dword:00000010 (16)
"Size of Read Buffers" =dword:00002000 (8192)
"Enable Buffered Writes" =dword:00000001 (1)
"Number of Write Buffers" =dword:00000010 (16)
"Size of Write Buffers" =dword:00002000 (8192)
"Write Thread Priority" =dword:00000001 (1)
"Read Thread Priority" =dword:00000001 (1)
Note: The performance improvements are still limited to resource usage (local to the media server, on backup target and on the transport layer) at the time of the backups!
Solution
The following registry keys can be modified to improve performance based on the configuration and setup of the media server. If the Media server has 8 CPU's and 12GB of memory then these values might be increased to see optimal performance. If the Media server has 2 CPU's and 4GB of memory then these values might need to be decreased to see optimal performance.
"Number of Read Buffers" and "Number of Write Buffers" can be increase to allow for additional buffers during the backup. The default value is 4 and can be increased or decreased by increments of 2.
"Size of Read Buffers" and "Size of Write Buffers" can be increased to allow for a larger buffer during the backup. The default value is Hexadecimal 400 and can be increased or decreased by increments of 200.
"Write Thread Priority" and "Read Thread Priority" Values are "0" normal, "1" above normal and "2" highest. Would not recommend to use any higher value than "1"!
Related Knowledge Base Articles
References
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Please note that this document is a translation from English, and may have been machine-translated. It is possible that updates have been made to the original version after this document was translated and published. Veritas does not guarantee the accuracy regarding the completeness of the translation. You may also refer to the English Version of this knowledge base article for up-to-date information.