一种迭代式快照系统的设计与实现

The Design and Implementation of an Iterative Snapshot System

VSVM是一个提供了迭代式快照机制的逻辑卷管理系统。该快照机制针对于普通应用,允许快照逻辑卷正常读写,支持对任意快照逻辑卷(可能是经过多次快照迭代操作产生的逻辑卷)继续创建快照。快照的可迭代性确保了对快照数据的高效灵活的管理。VSVM在快照逻辑卷的数据映射上采用了直接映射的方式,使得快照迭代操作次数的增加并不影响其处理复杂度,并在设计方面理论上消除了对快照操作迭代次数的限制。论文实现了VSVM的迭代快照原型并给出了性能分析。试验结果表明系统具有较强的快照性能,单个系统可以支持上百个迭代式快照逻辑卷的并发密集读写,迭代快照适于普通应用使用。

VSVM is a logical volume manager providing an ordinary-application-oriented iterative snapshot mechanism. In VSVM,any snapshot volume can be writable.No matter how many iterative operations have been produced in generating a snapshot volume,another snapshot based on it can still be created.This ensures that snapshot data can be managed efficiently and flexibly.We introduce a direct mapping method to snapshot volume data mapping,with which the complexity of snapshot logic won＇t be affected by the increase of iterative operations.This method also theoretically removes the limit of maximum number of snapshot iterative operations in design.We have implemented a VSVM prototype and analyzed its performance.Experimental results show that VSVM has nice snapshot performance;one single system can support concurrent intensive I/O on over one hundred iterative snapshot volumes.Therefore,the iterative snapshot volume is suitable for ordinary usage.