A primary storage array calculates signatures of chunks of production device data that are sent to a target device on a secondary storage array. The chunk signatures are sent to a signature device on the secondary storage array, where the chunk signatures are stored within the same LBA range on the signature device as their corresponding chunks are stored on the target device. Snaps of the target and signature device are created and associated as a snap pair. Later, the primary storage array calculates signatures of changed chunks of production device data that are sent to the target device. The changed chunk signatures are sent to the signature device. New snaps of the target and signature device are created and associated as a new snap pair. Chunk data is validated by calculating signatures of the chunks from the target device and comparing those signatures with the chunk signatures from the signature device.