Models and Software Model Checking of a Distributed File Replication System

Bjørner, Nikolaj

doi:10.1007/978-3-540-75221-9_1

Cited by 5 publications

(5 citation statements)

References 11 publications

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“…Bjørner [53] discusses the development of the Distributed File System Replication (DFS-R) component of Windows Server, during which a model checker found an issue with concurrent moves similar to Figure 2a. Bjørner outlines several possible solutions, but notes that model-checking their algorithm was not feasible due to state space explosion.…”

Section: Distributed Filesystemsmentioning

confidence: 99%

A Highly-Available Move Operation for Replicated Trees

Kleppmann

Mulligan

Gomes

et al. 2022

IEEE Trans. Parallel Distrib. Syst.

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Replicated tree data structures are a fundamental building block of distributed filesystems, such as Google Drive and Dropbox, and collaborative applications with a JSON or XML data model. These systems need to support a move operation that allows a subtree to be moved to a new location within the tree. However, such a move operation is difficult to implement correctly if different replicas can concurrently perform arbitrary move operations, and we demonstrate bugs in Google Drive and Dropbox that arise with concurrent moves. In this paper we present a CRDT algorithm that handles arbitrary concurrent modifications on trees, while ensuring that the tree structure remains valid (in particular, no cycles are introduced), and guaranteeing that all replicas converge towards the same consistent state. Our algorithm requires no synchronous coordination between replicas, making it highly available in the face of network partitions. We formally prove the correctness of our algorithm using the Isabelle/HOL proof assistant, and evaluate the performance of our formally verified implementation in a geo-replicated setting.

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Section: Distributed Filesystemsmentioning

confidence: 99%

A Highly-Available Move Operation for Replicated Trees

Kleppmann

Mulligan

Gomes

et al. 2022

IEEE Trans. Parallel Distrib. Syst.

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“…The state-based approaches keep track of the state of each file and directory, then the final states or deltas of the changed files and directories are propagated to the other sites to be merged there. Examples of this approach are Ficus [Reiher et al 1994], Coda [Kistler and Satyanarayanan 1992;Satyanarayanan et al 1990], Unison [Balasubramaniam and Pierce 1998], Andrew File System [Howard 1988;Kazar 1988], and Microsoft's DFS-R [Bjørner 2007].…”

Section: Existing Approachesmentioning

confidence: 99%

“…The inode approach models a file system as a collection of separate inodes (or database records as in the case of DFS-R [Bjørner 2007]). The namespace is stored in the directory inodes and data is stored in the file inodes.…”

Section: The Inode Approachmentioning

confidence: 99%

Merging semantics for conflict updates in geo-distributed file systems

Tao

Shapiro

Rancurel³

2015

Proceedings of the 8th ACM International Systems and Storage Conference

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We present our model of file systems and our merging semantics for resolving conflict updates in geo-distributed file systems. The system model fully describes a file system with all of its components including hard links. This model is able to identify all conflict cases which are classified into direct, such as concurrent updates to the same file, and indirect, such as cycles in the namespace of the file system. The merging semantics resolve all types of conflicts while being able to preserve the effect of all conflict updates. Our implementation of the system and the merging semantics outperforms the existing systems in terms of feature completeness.

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“…Move operations on the replicated tree are difficult to implement because concurrent operations by multiple clients may result in cycles; additionally, the tree structure may be broken [7], [8], [10]. Due to the concurrent operations, a concurrency control mechanism is required to ensure data correctness.…”

Section: Introductionmentioning

confidence: 99%

An Efficient Approach to Move Elements in a Distributed Geo-Replicated Tree

Anjana¹,

Chandrassery

Peri³

2022

2022 22nd IEEE International Symposium on Cluster, Cloud and Internet Computing (CCGrid)

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Replicated tree data structures are extensively used in collaborative applications and distributed file systems, where clients often perform move operations. Local move operations at different replicas may be safe. However, remote move operations may not be safe. We present an efficient algorithm to perform move operations on the distributed replicated tree while ensuring eventual consistency. The proposed technique is primarily concerned with resolving conflicts efficiently, requires no interaction between replicas, and works well with network partitions. We use the last write win semantics for conflict resolution based on globally unique operation timestamps. The proposed solution requires only one compensation operation to avoid cycles being formed when move operations are applied. The proposed approach achieves an effective speedup of 14.6−68.19× over the state-of-the-art approach in a geo-replicated setting.

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Models and Software Model Checking of a Distributed File Replication System

Cited by 5 publications

References 11 publications

A Highly-Available Move Operation for Replicated Trees

A Highly-Available Move Operation for Replicated Trees

Merging semantics for conflict updates in geo-distributed file systems

An Efficient Approach to Move Elements in a Distributed Geo-Replicated Tree

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