The effectiveness of deduplication on virtual machine disk images
The effectiveness of deduplication on virtual machine disk images
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DOI：
10.1145/1534530.1534540
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发表时间：
2009-05
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通讯作者：
Keren Jin;E. L. Miller
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作者：
Keren Jin;E. L. Miller
虚拟化正广泛部署在服务器中，以高效地提供许多逻辑上独立的执行环境，同时减少对物理服务器的需求。虽然这种方法节省了物理CPU资源，但它仍然消耗大量存储，因为每个虚拟机(VM)实例都需要自己的多GB磁盘映像。此外，现有系统不支持磁盘映像之间的自组织块共享，而是依赖诸如覆盖等技术来从单个“基本”映像构建多个VM。相反，我们建议使用重复数据消除来减少VM磁盘映像所需的总存储空间，并提高VM共享磁盘块的能力。为了测试重复数据删除的有效性，我们使用不同的分块策略对不同的虚拟机盘镜像集进行了广泛的评估。我们的实验发现，如果只更改区域设置或软件配置，在最初的几个虚拟磁盘映像之后，存储的数据量增长非常缓慢，当包含不同版本的操作系统或不同的操作系统时，压缩速度会受到影响。我们还表明，固定长度的块工作得很好，实现了几乎与可变长度块相同的压缩率。最后，我们展示了简单地识别填零的块，即使是在在线提供的现成的虚拟机盘映像中，也可以显著节省存储。
Virtualization is becoming widely deployed in servers to efficiently provide many logically separate execution environments while reducing the need for physical servers. While this approach saves physical CPU resources, it still consumes large amounts of storage because each virtual machine (VM) instance requires its own multi-gigabyte disk image. Moreover, existing systems do not support ad hoc block sharing between disk images, instead relying on techniques such as overlays to build multiple VMs from a single "base" image. Instead, we propose the use of deduplication to both reduce the total storage required for VM disk images and increase the ability of VMs to share disk blocks. To test the effectiveness of deduplication, we conducted extensive evaluations on different sets of virtual machine disk images with different chunking strategies. Our experiments found that the amount of stored data grows very slowly after the first few virtual disk images if only the locale or software configuration is changed, with the rate of compression suffering when different versions of an operating system or different operating systems are included. We also show that fixed-length chunks work well, achieving nearly the same compression rate as variable-length chunks. Finally, we show that simply identifying zero-filled blocks, even in ready-to-use virtual machine disk images available online, can provide significant savings in storage.