Modifying Copy-on-Write Space Size for Snapshots

The LVM (Linux) snapshot of the DDB hosted on a Linux machine requires a free space that must follow the given calculation:

5% of volume space as COW space and should be greater than or equal to 4GB and lesser than 50GB. That is:

If 5% of the volume space is less than 4GB, then it will use 4GB as COW space.

If 5% of the volume space is more than 50GB, then it will use 50GB as COW space.

This percentage also includes any free space requirement specified by your hardware vendor. However, the snapshot of the DDB hosted on a thin logical volume grows dynamically and shares space from thin pool if required free space is not available.

Create nSnapCowSizeMB additional settings to modify the COW space.


  1. From the CommCell Browser, expand Storage Resources > MediaAgents.
  2. Right-click the appropriate DDB Linux MediaAgent, and then click Properties.
  3. In the MediaAgent Properties dialog box, click the Additional Settings tab, and then click Add.
  4. In the Add Additional Settings on UNIX Client dialog box, in the Name box, type nSnapCowSizeMB.

    The Category and Type details are automatically populated.

  5. In the Value field, type 5120.

    Note 5120 (MB) is the example for the additional settings creation. This value should be 10% of the logical volume size.

    For example, if logical volume size is 200 GB, then the value should be 20480 (MB).

  6. Click OK and click OK to close MediaAgent Properties dialog box.

Last modified: 7/30/2019 9:04:34 PM