Disk encryption software
Disk encryption generally refers to wholesale encryption that operates on an entire volume mostly transparently to the user, the system, and applications. This is generally distinguished from file-level encryption that operates by user invocation on a single file or group of files, and which requires the user to decide which specific files should be encrypted. Disk encryption usually includes all aspects of the disk, including directories, so that an adversary cannot determine content, name or size of any file. It is well suited to portable devices such as laptop computers and thumb drives which are particularly susceptible to being lost or stolen. If used properly, someone finding a lost device cannot penetrate actual data, or even know what files might be present.
Array controller based encryption
The encryption of data can take place in many points in a storage network. The point of encryption may occur on the host computer, in the SAN infrastructure, the array controller or on each of the hard disks as shown on the diagram above. Each point of encryption has different merits and costs. Within the diagram, the key server components are also shown for each configuration of encryption. Designers of SANs and SAN components must take into consideration factors such as performance, deployment complexity, key server interoperability, strength of security, and cost when choosing where to implement encryption. But since the array controller is a natural central point of all data therefore encryption at this level is inherent and also reduces deployment complexity.