Implementing Backup and Recovery: The Readiness Guide for the Enterprise

NetBackup Network Performance

This section lists some factors to consider when you evaluate the network component of the NetBackup data transfer path to identify possible changes that may improve the overall performance of NetBackup.

• Network Load. There are two key considerations to monitor when you evaluate remote backup performance:

  • The amount of network traffic

  • The amount of time that network traffic is high

• Small bursts of high network traffic for short durations will have some negative impact on the data throughput rate. However, if the network traffic remains consistently high for a significant amount of time during the operation, the network component of the NetBackup data transfer path will very likely be the bottleneck. Always try to schedule backups during times when network traffic is low. If your network is heavily loaded, you may wish to implement a secondary network which can be dedicated to backup and restore traffic.

• NetBackup Media Server Network Buffer Size. The NetBackup media server has a tunable parameter that you can use to adjust the size of the Winsock2 network communications buffer used to receive data from the network (a backup) or write data to the network (a restore). This parameter specifies the value that is used to call the setsockopt() Winsock2 API to set the network buffer size for backups (SO_RCVBUF) and restores (SO_SNDBUF).

  The default value for this parameter in release 3.4.1 and earlier is 32032 bytes. In release 4.5, the default value for this parameter is derived from the NetBackup data buffer size (see below for more information about the data buffer size) using the following formula:

  For backup jobs: (<data_buffer_size> * 4) + 1024

  For restore jobs: (<data_buffer_size> * 2) + 1024

  Because the default value for the NetBackup data buffer size is 65536 bytes, this formula results in a default value of 263168 bytes for backups and 132096 bytes for restores.

  To set this parameter, create the following files:

  • <install_path>\NetBackup\NET_BUFFER_SZ

  • <install_path>\NetBackup\NET_BUFFER_SZ_REST

  • (new in 4.5, not used in earlier releases)

• These files contain a single integer specifying the network buffer size in bytes. For example, to use a network buffer size of 64 KB, the file would contain 65536. If the files contain the integer 0 (zero), the setsockopt() Winsock2 API call will be skipped and the system default value for the network buffer size will be used.

  If the NET_BUFFER_SZ file exists, its contents will be used to specify the network buffer size for both backup and restores.

  If the NET_BUFFER_SZ_REST file exists (only in 4.5), its contents will be used to specify the network buffer size for restores.

  If both files exist, the NET_BUFFER_SZ file will be used to specify the network buffer size for backups, and the NET_BUFFER_SZ_REST file will be used to specify the network buffer size for restores.

  Because local backup or restore jobs on the media server do not send data over the network, this parameter has no effect on those operations. It is used only by the NetBackup media server processes which read from or write to the network, specifically, the bptm or bpdm processes. It is not used by any other NetBackup for Windows processes on a master server, media server, or client.

  This parameter is the counterpart on the media server to the Communications Buffer Size parameter on the client, which is described below. The network buffer sizes are not required to be the same on all of your NetBackup systems for NetBackup to function properly, however, setting the Network Buffer Size parameter on the media server and the Communications Buffer Size parameter on the client (see below) to the same value has achieved the best performance in some NetBackup installations.

  Similarly, the network buffer size does not have a direct relationship with the NetBackup data buffer size (see below). They are separately tunable parameters. However, as you can see by the default value for network buffer size in release 4.5, setting the network buffer to a substantially larger value than the data buffer has achieved the best performance in many NetBackup installations.

  Tuning this parameter along with the Communications Buffer Size parameter on the client has resulted in significant improvements in the throughput of the network component of the NetBackup data transfer path in some NetBackup installations.

• NetBackup Client Communications Buffer Size. The NetBackup client has a tunable parameter that you can use to adjust the size of the Winsock2 network communications buffer used to write data to the network for backups. This parameter specifies the value that is used to call the setsockopt() Winsock2 API to set the network buffer size for backups (SO_SNDBUF).

  This parameter is the counterpart on the client to the Network Buffer Size parameter on the media server, described above. As mentioned, the network buffer sizes are not required to be the same on all of your NetBackup systems for NetBackup to function properly. However, setting the Network Buffer Size parameter on the media server (see above) and the Communications Buffer Size parameter on the client to the same value achieves the best performance in some NetBackup installations.

To set the Communications Buffer Size parameter:

1. From Host Properties in the NetBackup Administration Console in release 4.5, or from the Configure NetBackup GUI in earlier releases, open the Client Properties dialog for the client on which the parameter is to be changed.

2. From the Windows Client tab, set the Communications buffer size: field.

This parameter is specified in number of kilobytes. The default value is 32. An extra kilobyte is added internally for backup operations (SO_SNDBUF). Therefore, the default network buffer size for backups is 33792 bytes. In some NetBackup installations, this default value is too small. Increasing the value to 128 improves performance in these installations.

Another way to set this parameter is to configure the Buffer_Size parameter in the registry.

Locate the following key under HKEY_LOCAL_MACHINE

Software/VERITAS/NetBackup/CurrentVersion/Config

Add or modify the Buffer_Size value, which is a REG_DWORD value. Set it to 0x20.

Because local backup jobs on the media server do not send data over the network, this parameter has no effect on these local operations. This parameter is used by only the NetBackup client processes which write to the network, specifically, the bpbkar32 process. It is not used by any other NetBackup for Windows processes on a master server, media server, or client.