DeclStore: Layering is for the Faint of Heart


Popular storage systems support diverse storage abstractions by providing important disaggregation benefits. Instead of maintaining a separate system for each abstraction, unified storage systems, in particular, support standard file, block, and object abstractions so the same hardware can be used for a wider range and a more flexible mix of applications. As large-scale unified storage systems continue to evolve to meet the requirements of an increasingly diverse set of applications and next-generation hardware, de jure approaches of the past—based on standardized interfaces—are giving way to domain-specific interfaces and optimizations. While promising, the ad-hoc strategies characteristic of current approaches to co-design are untenable.

The standardization of the POSIX I/O interface has been a major success. General adoption has allowed application developers to avoid vendor lock-in and encourages storage system designers to innovate independently. However, large-scale storage systems are generally dominated by proprietary offerings, preventing exploration of alternative interfaces when the need has presented itself. An increase in the number of special-purpose storage systems characterizes recent history in the field, including the emergence of high-performance, and highly modifiable, open-source storage systems, which enable system changes without fear of vendor lock-in. Unfortunately, evolving storage system interfaces is a challenging task requiring domain expertise, and is predicated on the willingness of programmers to forfeit the protection from change afforded by narrow interfaces.

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