How to improve FlashBackup performance

You can adjust NetBackup FlashBackup performance in the following ways.

Table: Tips for improving FlashBackup performance

Tips	Notes
Assign the snapshot cache device to a separate hard drive	If using the FlashBackup feature with a copy-on-write method such as nbu_snap, assign the snapshot cache device to a separate hard drive. A separate hard drive reduces disk contention and the potential for head thrashing. Refer to the NetBackup Snapshot Client Administrator's Guide for more information on FlashBackup configuration.
Adjust the FlashBackup read buffer	If the storage unit write speed is fast, reading the client disk may become a bottleneck during a FlashBackup raw partition backup. By default, FlashBackup (on UNIX) reads the raw partition using fixed 128 KB buffers for full backups and 32 KB buffers for incrementals. FlashBackup-Windows, by default, reads the raw partition using fixed 32 KB buffers for full backups and for incrementals. In most cases, the default read buffer size allows FlashBackup to stay ahead of the storage unit write speed. To minimize the number of I/O waits when reading client data, you can tune the FlashBackup read buffer size. Tuning this buffer allows NetBackup to read continuous device blocks up to 1 MB per I/O wait, depending on the disk driver. The read buffer size can be adjusted separately for full backup and for incremental backup. In general, a larger buffer yields faster raw partition backup (but see the following note). In the case of VxVM striped volumes, the read buffer can be configured as a multiple of the striping block size: data can be read in parallel from the disks, speeding up raw partition backup. Note: Resizing the read buffer for incremental backups can result in a faster backup in some cases, and a slower backup in others. Experimentation may be necessary to achieve the best setting. The result of the resizing depends on the following factors: The location of the data to be read The size of the data to be read relative to the size of the read buffer The read characteristics of the storage device and the I/O stack. See Adjusting the read buffer for FlashBackup and FlashBackup-Windows.
Adjust the batch size for sending metadata to the catalog	See Adjusting the batch size for sending metadata to the NetBackup catalog.

Tips

Notes

Assign the snapshot cache device to a separate hard drive

If using the FlashBackup feature with a copy-on-write method such as nbu_snap, assign the snapshot cache device to a separate hard drive. A separate hard drive reduces disk contention and the potential for head thrashing.

Refer to the NetBackup Snapshot Client Administrator's Guide for more information on FlashBackup configuration.

Adjust the FlashBackup read buffer

If the storage unit write speed is fast, reading the client disk may become a bottleneck during a FlashBackup raw partition backup. By default, FlashBackup (on UNIX) reads the raw partition using fixed 128 KB buffers for full backups and 32 KB buffers for incrementals. FlashBackup-Windows, by default, reads the raw partition using fixed 32 KB buffers for full backups and for incrementals.

In most cases, the default read buffer size allows FlashBackup to stay ahead of the storage unit write speed. To minimize the number of I/O waits when reading client data, you can tune the FlashBackup read buffer size. Tuning this buffer allows NetBackup to read continuous device blocks up to 1 MB per I/O wait, depending on the disk driver. The read buffer size can be adjusted separately for full backup and for incremental backup.

In general, a larger buffer yields faster raw partition backup (but see the following note). In the case of VxVM striped volumes, the read buffer can be configured as a multiple of the striping block size: data can be read in parallel from the disks, speeding up raw partition backup.

Note:

Resizing the read buffer for incremental backups can result in a faster backup in some cases, and a slower backup in others. Experimentation may be necessary to achieve the best setting.

The result of the resizing depends on the following factors:

The location of the data to be read
The size of the data to be read relative to the size of the read buffer
The read characteristics of the storage device and the I/O stack.

See Adjusting the read buffer for FlashBackup and FlashBackup-Windows.

Adjust the batch size for sending metadata to the catalog

See Adjusting the batch size for sending metadata to the NetBackup catalog.

How to improve FlashBackup performance

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