Automatic and customisable checkpointing

A checkpointing mechanism by which in-memory data structures are copied from computation nodes (200) to staging nodes (700) by using RDMA, checkpoints are made and kept in memory in the staging node (700), and then asynchronously copied to non-volatile storage (150). In contrast to previous approaches, checkpoints remain in volatile memory (740) as part of the checkpointing mechanism. As a result, recovery from checkpoint is potentially faster, since the required checkpoint may be already in memory (740) in the staging node (700). An automatic and customisable mechanism is provided to control when the checkpointing process is triggered. As an alternative to copying an object through the network, the object in memory can be updated to a newer version of the object by applying the chain of changes made in the object in the corresponding computation node (200).