Dell PowerFlex 4.6.x Technical Overview

Rebuild

PowerFlex initiates a rebuild process in response to failure. Forward rebuild refers to creating a new copy of the data on another server. Backward rebuild refers to re-synchronizing one of the copies.

When a failure occurs, such as on a server, device or network failure, PowerFlex immediately initiates a process of protecting the data. This process is called rebuild, and comes in two flavors:

• Forward rebuild is the process of creating another copy of the data on a new server. In this process, all the devices in the storage pool work together, in a many-to-many fashion, to create new copies of all the failed storage blocks. This method ensures an extremely fast rebuild.
• Backward rebuild is the process of re-synchronization of one of the copies. This is done by passing to the copy only changes made to the data while this copy was inaccessible. This process minimizes the amount of data transferred over the network during recovery.

PowerFlex automatically selects the type of rebuild to perform. This implies that in some cases, more data will be transferred to minimize the time that the user data is not fully protected.