What factors affect the data transfer rate during a SQL Server backup or restore operation?

To optimize your system for SQL Server backups the first step is to tune your environment for standard backup operations. Details are provided in the NetBackup Backup Planning and Performance Tuning Guide. With this information as a background, you still must adjust several things specific to SQL Server. Note that some of the following factors are only applicable to SQL Server stream-based operations and have no affect on snapshot backups or restores. A detailed description of how to make these adjustments is available.

The following factors affect the data transfer rate during a SQL Server backup or restore operation.

MAXTRANSFERSIZE	(stream-based only) The size that SQL Server uses for transferring data. Among the SQL Server-specific factors, MAXTRANSFERSIZE has the greatest overall potential for optimizing transfer rates. In general, improved performance correlates directly with an increased MAXTRANSFERSIZE value.
NUMBER OF BUFFERS PER STRIPE	(stream-based only) Setting this factor to a value greater than one enables multi-buffer during data transfer. Multi-buffer prevents short-term producer-consumer imbalances during a backup or restore operation. Although you can set the number of buffers as high as 32, normally a value of 2 or 3 is sufficient. This setting corresponds to the NUMBUFS keyword. You can also use the BUFFERS keyword.
NUMBER OF STRIPES	You can improve performance if you increase the number of stripes that you use to back up a SQL Server object. You must meet the following requirements: Each stripe is backed up to a separate tape unit (the stripes are not multiplexed to the same drive). You have reached the maximum transfer rate of any single drive. Performance varies depending on your environment. Since each stripe uses individual threads, multiple stripes may lead to contention when they access internal SQL Server structures. A cost that is associated with management of the threads. However, you may see improvement on a large system if the cost to start starting and stop I/O is greater than using additional stripes.
SHARED MEMORY	Shared memory should always be used if it is available in your backup environment.
ALTERNATE BACKUP METHOD	(stream-based only) A transfer method in which SQL Server and NetBackup are allowed to share the same data transfer buffers. This method may not be faster than ordinary shared memory data transfer. But this method results in decreased CPU utilization because it avoids a data copy step. If you use ALTERNATE BACKUP METHOD, Symantec recommends that you have MAXTRANSFERSIZE set to the maximum value.