Continuous Backup Systems Utilizing Flash Memory

Main m e m o r y databases are promising approach t o realize high-performance sys tems without expensive special hardware. One serious problem is reliability and we need t o develop backup and recovery mechanisms suitable for m a i n m e m o r y . In order t o reduce overhead for backup operations, we have developed continuous backup mechanisms, which transmit data t o archive storage during utilization of main m e m ory without any software assistance. Flash memorybased storage can improve the e f ic iency over conventional disk sys tems, since it can realize fas ter read and write operations. A s sequential access i s performed by a series of direct accesses, the overhead caused by scheduling t o utilize sequential access is not required. One serious drawback of f lash memory i s the limit of the number of rewrite operations. W e have developed mechanisms which can realize f ive year lifetime by the current technology. Performance evaluation of the sys tems i s also presented.