Where are the values for SIZE_DATA_BUFFERS, NUMBER_DATA_BUFFERS and NET_BUFFER_SZ located on Windows NetBackup Servers?

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Where are the values for SIZE_DATA_BUFFERS, NUMBER_DATA_BUFFERS and NET_BUFFER_SZ located on Windows NetBackup Servers?


The purpose of this document is to clear up any issues surrounding the location and use of the NetBackup tuning parameters on Window Platform servers running NetBackup  versions 3.4.1 thru 6.0.

Windows Media Server - USE FILES:

SIZE_DATA_BUFFERS - Located in <install_path>\NetBackup\db\config directory

This is the size of the buffer that is used by bptm/bpdm processes (child/parent) to communicate with each other.  It is also the tape block size that bptm uses to write to tape.

NUMBER_DATA_BUFFERS - Located in the <install_path>\NetBackup\db\config directory  is a bptm setting to set the number of Data Buffers available to the bptm process for communication between the parent and the child .

NET_BUFFER_SZ - Located in the <install_path>\NetBackup directory is a bptm setting only. (The bptm child process uses this when communicating with bpbkar/tar). The NET_BUFFER_SZ value is for Windows Media Servers (a server with a storage device attached). The client equivalent is Buffer_Size which is located in the registry as a REG_DWORD value under the following path:

Windows Clients - USE REGISTRY:

Located in the Windows Registry, this value sets the size of the communication buffer (in kb) for the client processes (bpbkar32/tar32) when communicating to the bptm or bpdm process on the media server.

REG_DWORD: Buffer_Size: <Decimal value in KB>

NOTE: NetBackup client Buffer_Size KB value should match the Media Server NET_BUFFER_SZ byte value for optimal performance

After making changes, verify in the bptm troubleshooting log that the values have taken affect.

Example Values:


The media server BPTM Log will show something similar to the following:

Example output:

09:42:18.141 [920.728] <2> io_init: using 262144 data buffer size
09:42:18.141 [920.728] <2> io_init: CINDEX 0, sched Kbytes for monitoring = 30000
09:42:18.141 [920.728] <2> io_init: using 64 data buffers


The SIZE_DATA_BUFFER value specified must not exceed the maximum tape I/O block size supported by the both the tape drive or the HBA driver for the Operating System.
Symantec recommends checking with your tape device Vendor for maximum block I/O size.

Registry modification to the SCSI HBA driver may be required to allow block sizes larger than 64kb. Reference: MaximumSGList.

Using a SCSI RAID controller to connect a tape device is supported by Symantec NetBackup. However, most SCSI RAID cards do not support a block size larger that 64KB.

Check with your SCSI HBA vendor for maximum supported block size.


Terms of use for this information are found in Legal Notices.



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