I have a question regarding backups that is slow. I have a Windows 2003 standard server SP2 with Netbackup 6.5 we have installed a new LTO4 Dell library and the backups are still running at the same speeds it used to when we had an LTO2 library.
What I have noticed is that when my backups start the network card usage jumps to 99% and there it stays for the night. I have 2 network cards that are both forced to 1 GB and on the switch, the network cards are teamed. The CPU usage only peaks at 15% during the time that the backups run.
When I run only one job like exchange I get a transfer rate of 75 Mb/s but during the night when all the other backups run I get a transfer rate of 25 Mb/s on the same backup.
In general Ethernet bonding does not give duple up in performance, it more like a 1.5. Furthermore, once a session has started, it won't switch NIC card in the bundle until the session has ended. That causes issues in Netbackup environments where a lot of small sessions are established, but then explode when client start sending data.
After upgrading the drives from LTO2 to LTO4, you did any performance tunning for the tape drives. i also faced the same problem after upgading the tape library.
For most configurations, the default NetBackup buffer settings are correct and there is no need to adjust them for the purpose of performance. Furthermore, there are factors outside of NetBackup which effect performance and should be reviewed. Some of these external factors include Host Bus Adapter (HBA) cards, SCSI cards, network interface card (NIC) settings, client disk I/O speed, network latency, and tape drive I/O. All of these should be reviewed to determine their respective impact on backup and restore speeds prior to any attempts to tune NetBackup.
On a Windows server, four different buffer settings can be modified to enhance backup performance. Those settings are:
NUMBER_DATA_BUFFERS: The number of buffers used by NetBackup to buffer data prior to sending it to the tape drives. The default value is 16.
SIZE_DATA_BUFFERS: The size of each buffer setup multiplied by the NUMBER_DATA_BUFFERS value. The default value is 65536.
NET_BUFFER_SZ: The network receive buffer on the media server. It receives data from the client. The default value is 256K.
Buffer_size: The size of each data package sent from the client to the media server. The default value is 32K.