Offline Data Preparation

Offline data preparation is performed when the applications running on the host is not accessing data from the disk that is undergoing data preparation.

Figure 1-7 shows the SME Disk offline data preparation architecture.

Figure 1-7 SME Disk Offline Data Preparation Architecture

The offline data preparation involves the following actions:

• Quiescing the host applications by stopping the host I/O traffic.

• Backing up the clear data in the targeted disk. The backup can be to another disk or to an external tape. This backup is used to recover from errors.

• Server I/Os during the duration of the offline data preparation are rejected by the SME node.

Caution While host I/Os are blocked the host paths must be online during offline data preparation since the identity of the host port is used by the crypto engine. All DKR relationships that involves disk must be in disable state. Disk Key Replication (DKR) is used to manage remote replication relationships. For more information, see Configuring DKR.

Caution Disable all replication links of that disk before starting data preparation on the disk.

Caution Destroy older snapshots once the rekey is successful. The old snapshot can be kept as a backup to recover in case data preparation or rekey fails. Once successful, SME Disk does not support reading from older snapshots using previous keys.

• The offline data preparation is done by one SME node that uses the host identity of the selected path on which data preparation related I/Os are issued to the disk. During this process, I/Os to the targeted disk are failed back to the host with a SCSI check condition not ready. Server I/Os during the duration of the offline data preparation are sent back to the host as an SCSI check condition.

• Unquiescing the host applications. After the data preparation is completed, the applications running on the host are brought online to start access data from the encrypted crypto disk.