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Increasing Block Size

MediaAgents can write to media using different block sizes if the operating system and the hardware (HBA) that is associated with the MediaAgent on which the library is configured supports a higher block size. Increasing the block size increases the speed of write operations to tape media. The default block size for write operation is 64 KB. For mount paths, block size is the buffer size used for each write operation. (The File system allocation unit size is decided when the volume is formatted.)

Before increasing the block size, ensure that the following criteria are satisfied:

  • New block size is supported by the Host Bus Adapter Driver installed in the MediaAgent and the tape device. The most commonly used values are 128 KB or 256 KB.
  • All the MediaAgents that are associated with a Storage Policy support the block size that is configured on that storage policy
  • If different MediaAgents are used for backup and restore operations, and the backup MediaAgent has higher block size, then ensure that the restore MediaAgent is configured with Host Bus Adapters, and that tape drives that are able to read the data written with higher block size.
  • If you want to modify the block size, use the following supported values of block size:

    MediaAgent

    Supported Block Size

    ONTAP 6.5 NetApp Appliances*

    64 KB or lower

    DART 5.3 EMC filers*

    128 KB or lower

* If you specify a block size that is larger than the allowed limit, the NAS backup process automatically changes your entry to the maximum allowable block size.

Block sizes can be modified from the Data Path Properties dialog box available from the Data Paths tab of the Copy Properties dialog box, for the specific data path.

Last modified: 8/10/2018 3:28:26 PM