Improving Throughput for Small Disk Requests with Proximal I/O
Improving Throughput for Small Disk Requests with Proximal I/O
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发表时间：
2011-02
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通讯作者：
J. Schindler;Sandip Shete;Keith A. Smith
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作者：
J. Schindler;Sandip Shete;Keith A. Smith
本文介绍了一种提高文件系统随机磁盘I/O性能的新技术--近端I/O。实现近端I/O的关键技术是磁盘驱动器能够在一次旋转中淘汰分布在数十个磁道上的多个I/O。与传统的就地更新或随时随地写入文件系统相比，该技术可以将随机I/O性能提高近七倍，同时保持(接近)顺序的磁盘布局。本文量化了邻近I/O性能，并提出了一种简单的数据布局引擎，该引擎使用基于闪存的写缓存来聚合随机更新，直到它们具有足够的密度来利用邻近I/O。结果表明，仅使用基于磁盘的总存储容量的1%的缓存，就可以针对随机更新工作负载服务每转5.3个用户I/O请求。在陈旧的文件系统上，布局可以维持最好情况的3%以内的串行读取带宽。尽管使用闪存，但总体系统成本仅为具有所需磁盘轴数量以实现相同数量的随机I/O操作的系统的三分之一。
This paper introduces proximal I/O, a new technique for improving random disk I/O performance in file systems. The key enabling technology for proximal I/O is the ability of disk drives to retire multiple I/Os, spread across dozens of tracks, in a single revolution. Compared to traditional update-in-place or write-anywhere file systems, this technique can provide a nearly seven-fold improvement in random I/O performance while maintaining (near) sequential on-disk layout. This paper quantifies proximal I/O performance and proposes a simple data layout engine that uses a flash memory-based write cache to aggregate random updates until they have sufficient density to exploit proximal I/O. The results show that with cache of just 1% of the overall disk-based storage capacity, it is possible to service 5.3 user I/O requests per revolution for random updates workload. On an aged file system, the layout can sustain serial read bandwidth within 3% of the best case. Despite using flash memory, the overall system cost is just one third of that of a system with the requisite number of spindles to achieve the equivalent number of random I/O operations.