Abstract: The existing virtual disk image storage models are not suitable for the data sharing of large number of users in transparent computing platform due to the excessive redundant data. To solve the shortcoming, this paper proposes a tree virtual disk storage model (TVDSM) based on ROW (redirect-on-write). In the TVDSM, the virtual disk data resources are divided into multiple layers according to sharing degree, and different end-users share system resources and application software resources which are located in the upper layers, the model only stores self-rewritten data, thus greatly reduces the redundant data in virtual disk storage system. Then, this paper designs and implements a linking virtual disk storage structure based on bitmap index technology. The structure can not only well support the virtual disk storage model presented in the paper, but also support ROW and query location operation to realize separately with different granularity, which enables the system to obtain higher query efficiency in a smaller sharing granularity.

Key words: transparent computing, virtual disk image, redirect-on-write (ROW), bitmap

摘要： 为了解决在透明计算环境下，现有虚拟磁盘镜像存储存在多用户虚拟磁盘数据冗余过度的问题，基于写时重定向（redirect-on-write，ROW）思想设计了一种树状虚拟磁盘存储模型（tree virtual disk storage model，TVDSM）。该模型将虚拟磁盘中数据资源按共享度划分成多个层级，不同终端用户共享位于上层的系统资源以及应用软件资源，只在底层存储自身改写的数据，从而减少了虚拟磁盘存储系统中的冗余数据。同时基于位图索引技术设计并实现了一种树状的虚拟磁盘存储结构，该结构不仅能够很好地支持虚拟磁盘存储模型，而且支持将写重定向和查询定位操作以不同粒度分开实现，使得系统能够在较小共享粒度下获得较高的数据查询效率。

关键词: 透明计算, 虚拟磁盘镜像, 写时重定向（ROW）, 位图索引