To comply with a policy for a computing device indicating that data written by the computing device to the storage volume after activation of the policy be encrypted, an encrypted chunks map is accessed. The encrypted chunks map identifies whether, for each chunk of sectors of a storage volume, the sectors in the chunk are unencrypted. In response to a request to write content to a sector, the encrypted chunks map is checked to determine whether a chunk that includes the sector is unencrypted. If the chunk that includes the sector is unencrypted, then the sectors in the chunk are encrypted, and the content is encrypted and written to the sector. If the chunk that includes the sector is encrypted or not in use, then the content is encrypted and written to the sector.