The tape writing parameters (block size and cache size) allow you to fine-tune the software to achieve the maximum performance. Both parameters are required for writing to tapes, but normally you only need to adjust the block size. The optimal value depends on the tape device type and on the data being backed up, such as the number of files and their size.
Note When the software reads from a tape, it uses the same block size that was used when writing to the tape. If the tape device does not support this block size, the reading will fail.
The parameters are set on each machine that has a tape device attached. It can be a machine where an agent or a storage node is installed. On a machine running Windows, the configuration is performed in the registry; on a Linux machine, it is done in the configuration file /etc/Acronis/BackupAndRecovery.config.
In Windows, create the respective registry keys and their DWORD values. In Linux, add the following text at the end of the configuration file, right before the </registry> tag:
<key name="TapeLocation">
<value name="WriteCacheSize" type="Dword">
"value"
</value>
<value name=DefaultBlockSize" type="Dword">
"value"
</value>
</key>
DefaultBlockSize
This is the block size (in bytes) used when writing to tapes.
Possible values: 0, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576.
If the value is 0 or if the parameter is absent, the block size is determined as follows:
Registry key (on a machine running Windows): HKEY_LOCAL_MACHINE\SOFTWARE\Acronis\BackupAndRecovery\TapeLocation\DefaultBlockSize
Line in /etc/Acronis/BackupAndRecovery.config (on a machine running Linux):
<value name=DefaultBlockSize" type="Dword">
"value"
</value>
If the specified value is not accepted by the tape drive, the software divides it by two until the applicable value is reached or until the value reaches 32 bytes. If the applicable value is not found, the software multiplies the specified value by two until the applicable value is reached or until the value reaches 1 MB. If no value is accepted by the drive, the backup will fail.
WriteCacheSize
This is the buffer size (in bytes) used when writing to tapes.
Possible values: 0, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576, but not less than the DefaultBlockSize parameter value.
If the value is 0 or if the parameter is absent, the buffer size is 1 MB. If the operating system does not support this value, the software divides it by two until the applicable value is found or until the DefaultBlockSize parameter value is reached. If the value supported by the operating system is not found, the backup fails.
Registry key (on a machine running Windows):
HKEY_LOCAL_MACHINE\SOFTWARE\Acronis\BackupAndRecovery\TapeLocation\WriteCacheSize
Line in /etc/Acronis/BackupAndRecovery.config (on a machine running Linux):
<value name="WriteCacheSize" type="Dword">
"value"
</value>
If you specify a non-zero value that is not supported by the operating system, the backup will fail.