Dell PowerStore Importing External Storage to PowerStore Guide

Double fault

Double faults are defined as two separate fault events happening around the same time, such as the ones in the following examples:

• Paths from the host to the source go down and, around the same time, the connection between the PowerStore and the source system also go down.
• Both SPs of the source system go down during import.

For such rare case double faults, recovery is not fully automatic and manual intervention is needed. The recovery depends on the specific fault condition. Contact your service provider for resolution.

A single problem may manifest as a double fault where the recovery needs some manual intervention. For example, if the source system or volume goes out-of-service (for example, a source volume goes offline) during import, this problem manifests as a double fault. First, the import fails because PowerStore is not able to reach the source volume in the SAN path. The subsequent automatic cancel does not fully succeed since the host is not able to reach the source volume, it is offline. To recover, repair the source volume state, do any required cleanup, then try the import again.

PowerStore is a dual-node, multiappliance scale-out cluster. Typically, most failures in data unavailable are not fatal and handled by the inherent PowerStore cluster high availability design. The import orchestrator runs inside the PowerStore appliance and so the orchestrator is as highly available as PowerStore itself.

However, should there be an extreme case where a PowerStore cluster goes down during import before cutover, an option exists to recover and go back to the source system. Until this recovery, data is temporarily unavailable. The general idea is that you must do some manual intervention at the source system to clear the migration-specific states and then run the host platform-specific steps. Contact your service provider for such a recovery.

If an entire appliance is down, both nodes of the appliance are down. However, in a multiappliance cluster, ongoing imports continue in other running appliances. The imports, for which the destination volume is on that specific appliance which is down, get stalled. It is recommended that the appliance be brought up first before trying to cancel this stalled session.