Virtual machine replication and migration

Examples herein relate to checkpoint replication and copying of updated checkpoint data. For example, a memory controller coupled to a memory can receive a write request with an associated address to write or update checkpoint data and track updates to checkpoint data based on at least two levels of memory region sizes. A first level is associated with a larger memory region size than a memory region size associated with the second level. In some examples, the first level is a cache-line memory region size and the second level is a page memory region size. Updates to the checkpoint data can be tracked at the second level unless an update was previously tracked at the first level. Reduced amounts of updated checkpoint data can be transmitted during a checkpoint replication by using multiple region size trackers.