An apparatus, system, and method are disclosed for maintaining asynchronous mirroring. A detection module detects insufficient storage space to store a snapshot of a logical volume in at least one of a primary storage system and a secondary storage system. The primary storage system comprises the logical volume. A write from a host to the logical volume is acknowledged, maintaining asynchronous mode mirroring between the primary storage system and the host. The mirror module mirrors the write to the logical volume at the secondary storage system using a backup synchronous mode in response to detecting the insufficient storage space. Under the backup synchronous mode, the primary storage system acknowledges the write to the host while concurrently mirroring the write to the secondary storage system. The secondary storage system acknowledges the mirrored write to the primary storage system.