Efficient SSD Caching by Avoiding Unnecessary Writes using Machine Learning
Hua Wang, Xinbo Yi, Ping Sheng Huang, Bin Cheng, Ke Zhou · 2018
SSD has been playing a significantly important role in caching systems due to its high performance-to-cost ratio. Since cache space is much smaller than that of the backend storage by one order of magnitude or even more, write density (writes per unit time and space) of SSD cache is therefore much higher than that of HDD storage, which brings about great challenges to SSD's lifetime. Meanwhile, under social network workloads, quite a few writes on SSD are unnecessary, e.g., Tencent's photo caching shows that about 61% of total photos are just accessed once whereas they are still swapped in and out of the cache. Therefore, if we can predict this kind of photos proactively and prevent them from entering the cache, we can eliminate unnecessary SSD cache writes and improve cache space utilization.