CSR-DMSS,SM: Beyond Solid State Disks: Using FLASH to Save Energy in Enterprise Systems

能源效率正迅速成为企业系统设计的关键制约因素。到2011年，美国数据中心每年的能源消耗预计将增长到1000亿千瓦时以上，耗资74亿美元。其中多达40%的能量被DRAM和磁盘消耗。长期以来，电池寿命一直是便携式消费设备的关键问题，取而代之的是使用更快、更节能的闪存。闪存是非易失性的，待机功耗接近于零，每次读取闪存所需的功耗比读取DRAM低30倍，比磁盘访问低3个数量级。此外，闪存提供比磁盘低得多的访问延迟和更高的带宽，接近DRAM的性能水平。企业存储供应商最近发布了用大容量闪存固态磁盘（ssd）取代传统磁盘的产品。然而，由于它们是通过针对传统旋转磁盘优化的接口访问的，因此ssd无法充分利用闪存可以提供的低延迟和高带宽。此外，用ssd取代传统磁盘并不能解决服务器DRAM不断增长的功耗问题。在这个项目中，我们研究了更多的机会，除了ssd之外，通过在整个服务器的存储和内存层次中集成Flash，在企业系统中使用Flash节省能源。我们研究的长期目标——提高数据中心的能源效率——有可能大幅减少数据中心的碳足迹和对额外发电能力的需求。

Energy efficiency is rapidly becoming a key constraint in the design of enterprise systems. By 2011, yearly data center energy consumption in the United States is projected to grow to over 100 billion kWh at cost of $7.4 billion. As much as 40% of this energy is consumed by DRAM and disks. Portable consumer devices, where battery life has long been a key concern, instead use faster and more energy-efficient Flash storage. Flash is non-volatile, has near-zero standby power draw, and each Flash read requires 30x less power than a DRAM read and three orders-of-magnitude less power than a disk access. Moreover, Flash provides far lower access latency and higher bandwidth than disks, approaching DRAM performance levels. Enterprise storage vendors have recently announced products that replace traditional disks with high-capacity Flash solid-state disks (SSDs). However, because they are accessed through interfaces optimized for legacy rotating disks, SSDs fail to fully-exploit the low latency and high bandwidth Flash can provide. Furthermore, replacing conventional disks with SSDs does not address the growing power consumption of severs' DRAM. In this project, we examine further opportunities, beyond SSDs, to save energy with Flash in enterprise systems by integrating Flash throughout the servers' storage and memory hierarchies. The long term goal of our research--to improve data center energy efficiency--has the potential to drastically reduce the carbon footprint of data centers and the need for additional power generation capacity.