Fragmented Objects: Boosting Concurrency of Shared Large Objects

TL;DR

This paper introduces fragmented objects and a new consistency model to improve concurrency in distributed storage systems, demonstrated through a prototype file system called COBFS.

Contribution

It proposes fragmented linearizability and coverability for large shared objects, along with an implementation of COBFS that enhances concurrent access while maintaining strong consistency.

Findings

Preliminary emulation shows increased concurrency for large objects.

Fragmented linearizability ensures consistency across object fragments.

COBFS effectively manages large files with high concurrent access.

Abstract

This work examines strategies to handle large shared data objects in distributed storage systems (DSS), while boosting the number of concurrent accesses, maintaining strong consistency guarantees, and ensuring good operation performance. To this respect, we define the notion of fragmented objects:con-current objects composed of a list of fragments (or blocks) that allow operations to manipulate each of their fragments individually. As the fragments belong to the same object, it is not enough that each fragment is linearizable to have useful consistency guarantees in the composed object. Hence, we capture the consistency semantic of the whole object with the notion of fragmented linearizability. Then, considering that a variance of linearizability, coverability, is more suited for versioned objects like files, we provide an implementation of a distributed file system, called COBFS, that utilizes coverable fragmented objects (i.e., files).In COBFS, each file is a linked-list of coverable block objects. Preliminary emulation of COBFS demonstrates the potential of our approach in boosting the concurrency of strongly consistent large objects.