Onion and pizza: new disk partitioning schemes for virtualization systems

發表: SAC '13 Proceedings of the 28th Annual ACM Symposium on Applied Computing


The traditional disk partitioning scheme commonly used in a virtualization system divides a disk into multiple partitions in a coarse-grained manner, which causes a long seek distance when multiple virtual machines run concurrently. To overcome this drawback, we propose two novel schemes, called onion and pizza. The onion scheme makes partitions in an interleaved way, which leads to not only reduce a seek distance but also enhance fairness among virtual machines. The pizza scheme goes one step further that makes partitions in a vertical fashion, not a horizontal fashion, so that requests from different virtual machines can be served in a same cylinder. In additional, new sector mapping is devised for efficiency of the two schemes. Real implementation based experiments have shown that our proposal can enhance I/O bandwidth up to 95% with an average of 25%, compared with the traditional scheme.

原本 vm的disk partition 都要一整塊相連，如果很多vm，disk seek 可能很長 (例，disk head先被vm1拉走，然後vm4又發出 io request，但是vm4的partition離 vm1很遠~遠 )

他的方法就是
從coarse-grained manner的allocation方法，變成fined-grained (大塊 變 小塊啦啦)，再把 這一小小堆平均散開在整個disk中。依照散開的方法又分成 onion 和 pizza兩種 ，一個是水平地散(同磁盤)，一個是垂直地散

SH:
1 大塊變小塊什麼overhead嗎
2 怎麼散才能保証一定縮短 seek啊? 會不會反而更長 ?
3 有使用replication嗎，replication也是一種縮短seek的方法?  相比之下，有去分析優缺嗎?