Volume Reserve

Volume reserve is guaranteed physical space that is reserved for a volume. Reserved space is set aside for the volume and is immediately withdrawn from the general storage pool. Set the volume reserve to Thin Provisioning (no physical space is reserved) or Thick Provisioning (the entire physical space is reserved). As new data is written to a thickly provisioned volume, free space within the volume reserve decreases.

One consideration when setting volume sizes and reserves is the level of compression you get for a particular application or data set. For example, most volumes should see 50-75% compression, so a volume reserve of 10 GB will be able to store far more than the actual 10 GB space if it were uncompressed. In other words, 10 GB space of application data will only use between 2.5 GB and 5 GB when compressed.