SLAS: An efficient approach to scaling round-robin striped volumes
SLAS: An efficient approach to scaling round-robin striped volumes
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DOI：
10.1145/1227835.1227838
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发表时间：
2007-03
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通讯作者：
Guangyan Zhang;J. Shu;Wei Xue;Weimin Zheng
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作者：
Guangyan Zhang;J. Shu;Wei Xue;Weimin Zheng
循环条带化由于分布均匀、计算复杂度低，被广泛应用于需要高带宽和海量存储的应用中。由于许多系统在存储容量和 I/O 带宽需要增加时是不可停止的，因此一种高效的在线机制向条带卷添加更多磁盘非常重要。在本文中，提出并证明了在由于缩放循环条带卷而引起的数据重新分布期间，总是存在一个重新排序窗口，在该窗口中可以在改变数据移动顺序的同时保持数据一致性。此外，通过利用重排序窗口特性，SLAS被提出来扩展循环条带卷，有效降低了数据重新分配的成本。首先，SLAS应用了基于滑动窗口的新地图管理解决方案，支持数据重新分配，且不损失可扩展性；其次，它使用映射元数据的延迟更新来减少数据重新分配所需的元数据写入次数；第三，它改变数据块移动的顺序以聚合数据块的读/写。我们使用真实系统工作负载进行的详细模拟结果表明，与传统方法相比，SLAS 可以在前台 I/O 最大响应时间相似的情况下将重新分配持续时间缩短高达 40.79%。最后，我们的讨论表明 SLAS 方法适用于向条带卷添加磁盘以及从条带卷删除磁盘。
Round-robin striping, due to its uniform distribution and low-complexity computation, is widely used by applications which demand high bandwidth and massive storage. Because many systems are nonstoppable when their storage capacity and I/O bandwidth need increasing, an efficient and online mechanism to add more disks to striped volumes is very important. In this article, it is presented and proved that during data redistribution caused by scaling a round-robin striped volume, there is always a reordering window where data consistency can be maintained while changing the order of data movements. Furthermore, by exploiting the reordering window characteristic, SLAS is proposed to scale round-robin striped volumes, which reduces the cost of data redistribution effectively. First, SLAS applies a new mapping management solution based on a sliding window to support data redistribution without loss of scalability; second, it uses lazy updates of mapping metadata to decrease the number of metadata writes required by data redistribution; third, it changes the order of data chunk movements to aggregate reads/writes of data chunks. Our results from detailed simulations using real-system workloads show that, compared with the traditional approach, SLAS can reduce redistribution duration by up to 40.79% with similar maximum response time of foreground I/Os. Finally, our discussion indicates that the SLAS approach works for both disk addition and disk removal to/from striped volumes.