Volume Reserve

The volume reserve is the guaranteed minimum amount of physical space reserved for the volume. Reserved space is set aside for the volume and is immediately withdrawn from the general storage pool. Set the volume reserve from 100% (the entire physical space is reserved) to 0% (no physical space is reserved). As new data is written to the volume, the free space within the volume reserve decreases.You can increase the volume reserve if needed.

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 set to 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.