Browsing by Author "Hsu, ST"

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An implementation of using remote memory to checkpoint processes
(1999-09-01)
Hsu, ST
;
Chang, RC
;
資訊工程學系
;
Department of Computer Science
Process checkpointing is a procedure which periodically saves the process states into stable storage. Most checkpointing facilities select hard disks for archiving. However, the disk seek time is limited by the speed of the read-write heads, thus checkpointing process into a local disk requires extensive disk bandwidth. In this paper, we propose an approach that exploits the memory on idle workstations as a faster storage for checkpointing. In our scheme, autonomous machines which submit jobs to the computation server offer their physical memory to the server for job checkpointing. Eight applications are used to measure the remote memory performance in four checkpointing policies. Experimental results show that remote memory reduces at least 34.5 per cent of the overhead for sequential checkpointing and 32.1 per cent for incremental checkpointing. Additionally, to checkpoint a running process into a remote memory requires only 60 per cent of the local disk checkpoint latency time. Copyright (C) 1999 John Wiley & Sons, Ltd.
Continuous checkpointing: Joining the checkpointing with virtual memory paging
(1997-09-01)
Hsu, ST
;
Chang, RC
;
資訊工程學系
;
Department of Computer Science
Checkpointing is a basic mechanism for backward error-recovery in fault-tolerant systems. A checkpointed process stops execution and saves its states to files periodically. To reduce the file sizes, only data modified between two consecutive checkpoint times is saved. However, existing approaches do not consider operating system paging activities; which, if ignored may double the number of disk accesses required to checkpoint non-resident dirty pages. In this paper, we propose continuous 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 longer proportional to application size, but rather is bounded by resident dirty pages. Experimental results show that disk accesses can be reduced by about 80% when checkpointing large applications. (C) 1997 by John Wiley & Sons, Ltd.