Systems and methods to avoid deadlock and guarantee mirror consistency during online mirror synchronization and verification

摘要

Systems and methods can provide mirrored virtual targets and online synchronization and verification of the targets while avoiding deadlock, inconsistencies between members of the target, and false verification failures. A lock within the storage switch can limit the number of outstanding commands for a physical target to one during synchronization and verification operations. In one embodiment, a lock can be implemented as one or more resource tables maintaining an indication of the number of transfer ready signals available from physical targets. During typical write operations, deadlock can be avoided by determining whether each physical target for the mirrored operation can issue a transfer ready signal prior to issuing a command to the physical target. When a synchronization or verification operation begins, the maximum available number of transfer ready signals for each target can be decremented to one in order to limit the total number of outstanding commands for each target to one.