CONTINUOUS CHECKPOINTING - JOINING THE CHECKPOINTING WITH VIRTUAL MEMORY PAGING

Checkpointing is a basic mechanism for backward error-recovery in faul t-tolerant systems. A checkpointed process stops execution and saves i ts states to files periodically. To reduce the file sizes, only data m odified between two consecutive checkpoint times is saved. However, ex isting approaches do not consider operating system paging activities; which, if ignored may double the number of disk accesses required to c heckpoint non-resident dirty pages. In this paper, we propose continuo us checkpointing, which combines the checkpoint facility with virtual memory paging operations. Thus, checkpointing is continuous during the Lifetime of a process without extra overhead. Checkpoint size is no l onger proportional to application size, but rather is bounded by resid ent dirty pages. Experimental results show that disk accesses can be r educed by about 80% when checkpointing large applications. (C) 1997 by John Wiley & Sons, Ltd.