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Storage capacity demand is projected to grow exponentially in the coming decade and so will its contribution to the overall carbon footprint of computing devices. In recent years, cloud providers and device vendors have substantially reduced their carbon impact through improved power consumption and product distribution. However, by 2030, the manufacturing of flash-based storage devices will account for 1.7% of carbon emissions in the world. Therefore, reducing production-related carbon emissions of storage is key to sustainability in computing devices. We present Sustainability-Oriented Storage (SOS), a new host-device co-design for personal storage devices, which opportunistically improves storage sustainability by: (1) targeting widely-produced flash-based personal storage devices; (2) reducing hardware production through optimizing bit density in existing materials, up to 50%; and (3) exploiting an underutilized gap between the effective lifespan of personal devices and longer lifespan of their underlying flash. SOS automatically stores low-priority files, occupying most personal storage capacities, on high-density flash memories, currently designated for nearline storage. To avoid data loss, low-priority files are allowed to slightly degrade in quality over time. Switching to high-density memories, which maximize production material utilization, reduces the overall carbon footprint of personal storage devices. 

Peripheral devices like SSDs are growing more complex, to the point they are effectively small computers themselves. Our position is that this trend creates a new kind of attack vector, where untrusted software could use peripherals strictly as intended to accomplish unintended goals. To exemplify, we set out to rowhammer the DRAM component of a simplified host-side FTL, issuing regular I/O requests that manage to flip bits in a way that triggers sensitive information leakage. We conclude that such attacks might soon be feasible, and we argue that systems need principled approaches for securing peripherals against them. 

Although flash cells wear out, a typical SSD has enough cells and sufficiently sophisticated firmware that its lifetime generally exceeds the expected lifetime of its host system. Even under heavy use, SSDs last for years and can be replaced upon failure. On a smartphone, in contrast, the hardware is more limited and we show that, under heavy use, one can easily, and more quickly, wear out smartphone flash storage. Consequently, a simple, unprivileged, malicious application can render a smartphone unbootable ("bricked") in a few weeks with no warning signs to the user. This bleak result becomes more worrisome when considering the fact that smartphone users generally believe it is safe to try out new applications. To combat this problem, we study the I/O behavior of a wide range of Android applications. We find that high-volume write bursts exist, yet none of the applications we checked sustains an average write rate that is high enough to damage the device (under reasonable usage assumptions backed by the literature). We therefore propose a rate-limiting algorithm for write activity that (1) prevents such attacks, (2) accommodates "normal" bursts, and (3) ensures that the smartphone drive lifetime is longer than a preconfigured lower bound (i.e., its warranty). In terms of user experience, our design only requires that, in the worst case of an app that issues continuous, unsustainable, and unusual writes, the user decides whether to shorten the phone's life or rate limit the problematic app. 

Even on modern SSDs, I/O scheduling is a first-order performance concern. However, it is unclear how best to optimize I/O patterns for SSDs, because a complex layer of proprietary firmware hides many principal aspects of performance, as well as SSD lifetime. Losing this information leads to research papers drawing incorrect conclusions about prototype systems, as well as real-world systems realizing sub-optimal performance and lifetime. It is our position that a useful performance model of a foundational system component is essential, and the community should support efforts to construct models of SSD performance. We show examples from the literature and our own measurements that illustrate serious limitations of current SSD modeling tools and disk statistics. We observe an opportunity to resolve this problem by reverse engineering SSDs, leveraging recent trends toward component standardization within SSDs. This paper presents a feasibility study and initial results to reverse engineer a commercial SSD's firmware, and discusses limitations and open problems.