Deterministic service guarantees for nand flash using partial block cleaning
Deterministic service guarantees for nand flash using partial block cleaning
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DOI：
10.1145/1450135.1450141
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发表时间：
2008-10
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通讯作者：
Siddharth Choudhuri;T. Givargis
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作者：
Siddharth Choudhuri;T. Givargis
NAND闪存的特性（如批量擦除和磨损均衡）导致非线性和不可预测的读/写访问时间。在应用领域的情况下，如流媒体和实时系统，一个确定性的读/写访问时间是在设计时所需的。我们提出了一种新的NAND闪存转换层，称为GFTL，它保证了固定的上限（即，最坏情况服务率），用于与理论上的理想情况相当的读和写。通过消除GFTL设计中的非确定性来源和使用部分块清理，可以实现这种保证。GFTL通过将单个块的垃圾收集划分为几个块来执行部分步骤的垃圾收集，从而在服务请求时交错和隐藏垃圾收集延迟。此外，GFTL保证与闪存利用率、大小或状态无关。沿着理论界限，基准测试结果表明我们的方法的有效性。根据我们的实验，GFTL需要额外的16%的总块用于闪存管理。GFTL服务保证可根据闪存规格计算。因此，使用GFTL，设计人员可以在设计时先验地确定服务保证和大小要求。
NAND flash idiosyncrasies such as bulk erase and wear leveling results in non-linear and unpredictable read/write access times. In case of application domains such as streaming multimedia and real-time systems, a deterministic read/write access time is desired during design time. We propose a novel NAND flash translation layer called GFTL that guarantees fixed upper bounds (i.e., worst case service rates) for reads and writes that are comparable to a theoretical ideal case. Such guarantees are made possible by eliminating sources of non-determinism in GFTL design and using partial block cleaning. GFTL performs garbage collection in partial steps by dividing the garbage collection of a single block into several chunks, thereby interleaving and hiding the garbage collection latency while servicing requests. Further, GFTL guarantees are independent of flash utilization, size or state. Along with theoretical bounds, benchmark results show the efficacy of our approach. Based on our experiments, GFTL requires an additional 16% of total blocks for flash management. GFTL service guarantees can be calculated from flash specifications. Thus, with GFTL, a designer can determine the service guarantees and size requirements apriori, during design time.