Symantec Backup Exec

Caution:

Preferred configuration settings are used to tune the performance of backup and restore operations. Changing preferred configuration settings is not generally recommended and may have a negative effect on your backup and system performance. Any changes should be thoroughly tested to make sure that system performance does not deteriorate.

Enable compression

Indicates if hardware compression is enabled.

If this option is available, this device is capable of supporting hardware compression.

If a job is configured to use hardware compression, but is run on a device on which hardware compression is disabled (even though it is supported), hardware compression is considered unavailable and is not used.

Block size (per device)

Displays the size of the blocks of data that are written to new media in this device. The default is the preferred block size.

Some devices (for example, LTO devices) provide better performance when larger block sizes are used. The preferred block size can range from 512 bytes to 64 kilobytes or larger. If you use a device that supports larger block sizes, you can change the device’s block size in the Device Configuration tab. However, if the option to change the block size is unavailable, you must configure the device to use a larger size.

See the device manufacturer’s documentation for help in configuring the device.

Backup Exec does not ensure that the requested block size is in fact supported by that device. You should check the device specifications to make sure that the block size is supported. If the device does not support a block size, it will default to its standard block size.

If the device does not support block size configuration, this option is unavailable.

Buffer size (per device)

Displays the amount of data sent to the device on each read or write request. The buffer size must be an even multiple of the block size.

Depending on the amount of memory in your system, increasing this value may improve device performance. Each type of device requires a different buffer size to achieve maximum throughput.

Buffer count

Displays the number of buffers allocated for this device.

Depending on the amount of memory in your system, increasing this value may improve device performance. Each type of device requires a different number of buffers to achieve maximum throughput.

If you change the buffer count, you may need to adjust the high water count accordingly.

High water count

Displays the number of buffers to be filled before data is first sent to the device, and any time after that if the device underruns.

The high water count cannot exceed the buffer count. A value of 0 disables the use of high water logic; that is, each buffer is sent to the device as it is filled.

The default setting provides satisfactory performance in most instances; in some configurations, throughput performance may be increased when other values are specified in this field. If you increase or decrease the buffer count, the high water count should be adjusted accordingly. If a device has a high water count default of 0, it should be left at 0.

Default Settings

Returns all of the preferred configuration settings to their defaults.

Read single block mode

Indicates if this device reads only one block of data at a time, regardless of the size of the buffer block.

Write single block mode

Indicates if this device writes only one block of data at a time. This option provides greater control over the handling of data write errors.

Symantec recommends this option if the device is a shared storage device.

Read SCSI pass-through mode

Indicates if this device reads data without going through a Microsoft tape device API. This option allows the data to pass directly through the device and allows more detailed information if device errors occur.

Write SCSI pass-through mode

Indicates if this device writes data without going through the Microsoft tape device API. This option allows data to pass directly through the device driver and allows more detailed information if device errors occur.

Symantec recommends this option if the device is a shared storage device.