Nonstop Volume Level Encryption Guide

3 Encrypting data on storage devices
This section describes how to encrypt data on disk drive and tape devices. Only the security officer
can enable or disable encryption.
Encrypting data on disk drives
These procedures describe how to encrypt data on disk drives. Each disk has a unique encryption
key, which means that primary and mirror disks of a mirrored volume will have different encryption
keys. The CLIM performs the disk data encryption and decryption.
You can encrypt data either by using REVIVE key rotation, or CLIM key rotation. Both techniques
are cable of initial encryption, key rotation, and decryption.
During a REVIVE key rotation the mirror disk is down, which implies a loss of fault tolerance. During
CLIM key rotation, one path to the mirror disk remains up so that fault tolerance is preserved. The
CLIM performs the key rotation and processor performance is not affected. Multiple disks can be
encrypted concurrently.
CAUTION: For mirrored drives, HP recommends that you use CLIM key rotation because it is
more fault tolerant and the data is not passed through the host system. If a CLIM key rotation fails
for any reason, use REVIVE key rotation to recover. You should consider not using unmirrored
drives for encryption, but if you use them, you must use CLIM key rotation. If CLIM key rotation
fails on an unmirrored disk, there is no way to recover the data.
Encrypting disk data with CLIM key rotation
This section describes how to encrypt data on disks with CLIM key rotation.
CLIM key rotation is performed by doing a CLIM key change. It can change data on a disk from
unencrypted to encrypted, from encrypted to unencrypted, or from encrypted to encrypted with a
new key. This encryption method is fault tolerant. The primary and mirror disk are both up during
the encryption, although one path to the mirror is down. This method is the only way to encrypt
an un-mirrored disk.
The time required to perform a key change depends on the amount of data on the disk.
If a CLIM key change failure occurs (that is, the CLIM fails during the key change operation), the
disk must be revived from its mirror or recovered from backup. Therefore, HP recommends that the
disk should be mirrored before key rotation is performed. Only the security officer can enable or
disable encryption, or revive a disk. An operator can perform a revive but cannot change the
encryption attributes of a disk.
Overview
In a typical fault tolerant system there is a primary and a mirror disk, each attached to two CLIMs,
with four paths, as shown in Figure 2:
44 Encrypting data on storage devices