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Introduction to NetBackup for SQL Server Technical overview

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 impact on snapshot backups or restores.

Detailed descriptions of how to make the adjustments are described in Performance factors” on page 45.

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.

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.

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