标题: | 缓和在多通道下自我治愈结构之固态硬碟的治愈风暴问题 Mitigating the heal storm problem in multi-channel self-healing SSDs |
作者: | 周昆霖 张立平 Chou, Kun-Lin Chang, Li-Ping 资讯科学与工程研究所 |
关键字: | 快闪记忆体;自我治愈;磨损平均;快闪记忆体寿命;NAND flash memory;self-healing;wear leveling;flash lifetime |
公开日期: | 2017 |
摘要: | 为了降低每个位元的价位,快闪记忆体的储存密度越来越高,这会造成快闪记忆体的寿命越来越低,而这也是快闪记忆体要能普及所需关注的重要议题,近来的研究指出损坏的区块可以藉由自我治愈来增加快闪记忆体的寿命,然而传统磨损平均被用来平衡所有区块的抹擦次数,也就是说所有几乎所有区块会在同一时间自我治愈,我们称这集中治愈的问题为治愈风暴,治愈风暴会造成较高的反应时间、较差的稳定性还有突然急遽升高的耗电量,得益于传统磨损平均可以平衡区块抹擦次数的特性,我们在每个区块加上一个拥有不同初始值的虚拟抹擦次数,并且让传统的磨损平均作用在上面,藉由如此我们可以让所有区块的抹擦次数分布在一个可控的范围内并藉此分散区块治愈的时机,我们还有提出一个方法用较早的去做区块治愈来避免读请求会被区块治愈所卡住,并且我们的方法可以以几乎没有额外负担的情况下做在现有的快闪记忆体转换层和磨损平均演算法上,在我们的实验中我们测试了许多不同的测资,我们成功的呈现了我们的方法在没有影响快闪记忆体寿命的前提下解决了治愈风暴的问题。 The flash storage density continues to increase because of high cost per bit. However, it causes worse flash endurance and short life time is a critical issue of the popularity of NAND flash memory. Recent studies show that worn-out block can be healed by heat-accelerated self-recovery to extend flash life time. However, the erase counts of all blocks are balanced under conventional wear leveling, and thus all blocks would heal almost at the same time. We call intensive block healing as a heal storm. A heal storm may result in bad response time and throughput, poor reliability, and instantaneously high power consumption. Inspired by evening distribution of erase counts under conventional wear leveling, we add a virtual erase count to each block with a different initial value and let conventional wear leveling operate on it. In this way, the distribution of erase counts would be distributed in a control interval and therefore disperse the healing time. We further propose a method to do block healing earlier to avoid read requests blocked by heal commands. Moreover, our approach can apply on existing FTL design and wear leveling algorithm with almost no extra overhead. In our experiments, we successfully show that our approach solves the heal storm problem without affecting the flash life time under different kinds of workloads. |
URI: | http://etd.lib.nctu.edu.tw/cdrfb3/record/nctu/#GT070356068 http://hdl.handle.net/11536/140303 |
显示于类别: | Thesis |