Specify the Block Size for Backups to Tape Drives

Arcserve Backup lets you specify the block size for tape backups. This capability lets Arcserve Backuptransfer more data per block to the device. Before you specify a larger tape block size, consider the following circumstances:

• The largest default tape block that Arcserve Backup can transfer is 64 KB. You can increase the tape block size to 128 KB, 256 KB, or 512 KB when using tape drives in your backup environment that support larger tape blocks.
• Note: See the device and host bus adapter (HBA) manufacturer documentation to verify that the device supports larger data transfers.
• Large block backups require HBAs that support large transfer sizes. When Arcserve Backup detects the HBA cannot support the data transfer size required for the larger block size, Arcserve Backup disables the larger block size and records an error message in the Tape engine log file.
• When Arcserve Backup overwrites or uses blank tapes, Arcserve Backup formats the media using the newly defined tape block size.
• When Arcserve Backup appends data to media, Arcserve Backup writes the appended data to the media using the block size originally applied to the media.
• For SAN attached libraries, verify that the HBA for all SAN member servers can support the transfer size that the tape block size requires. Backups to SAN member servers that do not support the larger transfer size usually fail.

To specify the tape block size for tape drives

1. Stop the Arcserve Backup Tape Engine service on the backup server that you want to configure.
2. Open Windows Registry Editor and browse to the following:
   • x86 platforms:

   HKEY_LOCAL_MACHINE\SOFTWARE\ComputerAssociates\CA ARCServe Backup\Base\TapeEngine

   • x64 platforms:

   HKEY_LOCAL_MACHINE\SOFTWARE\ComputerAssociates\CA ARCServe Backup\Base\TapeEngine

3. Locate the DEVICE# key for the tape drive that you want to configure.
4. Under the DEVICE# key, create a DWord registry key named ForceBlockSize.
5. Specify one of the following DWORD values:
   • 128 KB: 0x80
   • 256 KB: 0x100
   • 512 KB: 0x200
6. Close the Edit DWORD Value dialog and close Windows Registry Editor.
7. Restart the Arcserve Backup Tape Engine service.

The tape block size is applied to the tape drive.