About tuning parameters for SQL Server backups

The Microsoft SQL Server tab contains the tuning parameters that can improve the performance of your backups. These settings, and other factors that affect performance, are discussed in this topic.

See NetBackup for SQL Server performance factors.

Caution:

Do not enable multiplexing if the policy is also configured with multiple stripes. Restores fail when both multiplexing and multiple stripes are configured for a backup policy.

Table: Tuning parameters for SQL Server backups

Field	Description
Number of backup stripes	This option divides the backup operation into multiple concurrent streams. A stream corresponds to a job in the activity monitor. For example, if the value is 3, each database is backed up using three jobs. This configuration applies in any situation in which SQL Server dumps data faster than your tape drive is capable of writing. The default value for this option is 1. Range is 1 - 32. See Configuring multistriped backups of SQL Server.
Client buffers per stripe	(Stream-based backups only) This option affects buffer space availability. NetBackup uses this parameter to decide how many buffers to allocate for reading or writing each data stream during a backup operation. By allocating a greater number of buffers, you can affect how quickly NetBackup can send data to the NetBackup master server. The default value for this option is 2, which allows double buffering. You may get slightly better performance by increasing this value to a higher value. Range is 1 - 32.
Maximum transfer size	(Stream-based backups only) This option is the buffer size used by SQL Server for reading and writing backup images. Generally, you can get better SQL Server performance by using a larger value. This option can be set for each backup operation. Calculated as 64 KB * 2^MAX_TRANSFER_SIZE. It ranges in size from 64 KB to 4 MB. The default is 4 MB.
Backup block size	This option applies to stream-based backups only. Sets the incremental size that SQL Server uses for reading and writing backup images and can be set for each backup operation. Calculated as 512 bytes * 2^BLOCK_SIZE. The value for this option ranges from 0.5 KB to 64 KB. The default is 64 KB.
Parallel backup operations	This option is the number of backup operations to start simultaneously, per database instance. Range is 1 - 32. The default is 1. You may need to configure other options when you configure two or more parallel backup operations. See Configure the number of jobs allowed for backup operations.
Microsoft SQL Server checksum	Choose one of the following options for SQL Server backup checksums: None. Disables backup checksums. To verify the checksums before the backup, choose one of the following options. Note that these options impose a performance penalty on a backup or restore operation. Continue on error. If the backup encounters a verification error, the backup continues. Fail on error. If the backup encounters a verification error, the backup stops.
Use Microsoft SQL Server compression	Enable this option to use SQL Server to compress the backup image. If you enable SQL Server compression, do not enable NetBackup compression. SQL Server compression is not supported for snapshot backups.
Skip unavailable (offline, restoring, etc.) databases	NetBackup skips any database with a status that prevents NetBackup from successfully backing up the database. These statuses include offline, restoring, recovering, and emergency mode, etc. NetBackup skips the backup of the unavailable database, but continues with the backup of the other databases that the policy includes. The backup completes with a status 0 and the job details indicate that the database was skipped. See Schedule backup types for SQL Server Intelligent Policies.
Copy-only backup	This option allows SQL Server to create an out-of-band backup so that it does not interfere with the normal backup sequence. The default value is cleared except for full database Instant Recovery backups. See Using copy-only snapshot backups to affect how differentials are based.
Skip read-only file groups	This option excludes any filegroups that are read-only from the backup. The resulting backup is a partial image because the image does not contain all filegroups. The partial image contains data from the read-write filegroups and data from the primary filegroup. This option applies only to the Whole database backup selection. See Backing up read-write filegroups.
Convert differential backups to full (when no full exists)	If no previous full backup exists for the database or filegroup, then NetBackup converts a differential backup to a full backup. The agent checks to determine if a full backup exists for each database. If no previous full backup exists, a differential backup is converted to a full as follows: If you select a database for a differential backup, the backup is converted to a full database backup. If the Skip read-only file groups option is selected the backup is converted to a full read/write filegroup backup. If you select a filegroup for a differential backup, NetBackup does the following: If the filegroup is the default database filegroup, NetBackup converts the backup to a full filegroup backup. If the filegroup is a secondary filegroup and a backup of the primary filegroup does not exist, NetBackup converts the backup to a partial full database backup. This backup contains the selected filegroup and default filegroup. If the filegroup is a secondary filegroup and a backup of the primary filegroup does exist, NetBackup converts the backup to a full filegroup backup of the selected filegroup. For snapshot backup policies, you must create a Full backup schedule for NetBackup to successfully convert differential backups to full backups. Note: NetBackup only converts a differential backup if a full backup was never performed on the database or filegroup. If a full backup does not exist in the NetBackup catalog but SQL Server detects an existing full LSN, NetBackup performs a differential backup and not a full. In this situation, you can restore the full backup with native tools and any differentials with the NetBackup MS SQL Client. Or, if you expired the backup in NetBackup, you can import the full backups into the NetBackup catalog. Then you can restore both the full and the differential backups with the NetBackup MS SQL Client.
Truncate logs after backup	This option backs up the transaction log and removes the inactive part of the transaction log. This option is enabled by default.
Convert log backups to full (when no full exists)	If no previous full backup exists for the database, then NetBackup converts a transaction backup to a full backup. This option also detects if a full recovery database was switched to the simple recovery model and back to the full recovery model. In this scenario, the log chain is broken and SQL Server requires a differential backup before a subsequent log backup can be created. If NetBackup detects this situation, the backup is converted to a differential database backup. Note: NetBackup only converts a transaction log backup if a full backup was never performed on the database. If a full backup does not exist in the NetBackup catalog but SQL Server detects an existing full LSN, NetBackup performs a transaction log backup and not a full. In this situation, you can restore the full backup with native tools and any differentials and log backups with the NetBackup MS SQL Client. Or, if the backup was expired by NetBackup, you can import the full backups into the NetBackup catalog. Then you can restore the full, differential, and log backups with the NetBackup MS SQL Client.
Availability database backup preference	The selection on the Select instances and databases tab determines the options you can select in this list. None and Skip availability databases are only available for instances and instance groups. None Perform the backup on the specified instance. Protect primary replica Backups always occur on the primary replica. This option applies to availability replicas and to instances that have both standard databases and availability databases. Protect preferred replica Honors your SQL Server backup preferences. These preferences include the preferred replica, backup priority, and excluded replicas. Note that NetBackup initiates a backup job on each replica. The backup is skipped on any replica that isn't the intended backup source. This option applies to availability replicas and to instances that have both standard databases and availability databases, Skip availability databases Skips any availability databases on the instance. Use this option to protect only the databases that are not part of an availability group when the policy includes any instances that contain both standalone databases and availability databases.
VDI yimeout (seconds)	Determines the timeout interval for SQL Server Virtual Device Interface. The selected interval is applied to backups and restores of databases and of transaction logs. The default value for backups is 300. The default value for restores is 600. Range is 300 - 2147483647.
Group size for snapshots	This option quiesces a group of databases together and creates a snapshot to back them up as a group. NetBackup automatically discovers and groups any databases that can be grouped, up to this value. A separate snapshot is created for the master database. If both availability databases and standard databases are included in the same policy, separate snapshots are created for each availability group and for the standard databases. If the limit is reached, NetBackup creates additional snapshots. The default value is 1. Range is 1 to 64.

More Information

Backing up read-only filegroups

About tuning parameters for SQL Server backups

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