Coordinated checkpointing has low stable storage requirements and simplifies the recovery process by reserving a set of consistent global checkpoints. Unfortunately, most algorithms that were proposed either incurred a high communication overhead or blocked all processes. Then, a coordinated algorithm was presented which was nonblocking and which forced only a subset of all processes to participate in a checkpointing event. This algorithm was shown to create inconsistencies in some situations and new algorithms to take consistent checkpoints were proposed. However, we found that these algorithms can still result in inconsistencies when typical behavior in a distributed environment is considered, such as multiple forced checkpoints and multiple concurrent checkpoint initiations. In this paper we identify the inconsistencies that can occur and present an efficient nonblocking algorithm that collects consistent global checkpoints and avoids some of the pitfalls in distributed nonblocking checkpointing.

No abstract

A mobile computing system consists of mobile and stationary nodes. Checkpointing in mobile systems faces many new challenges, such as low wireless bandwidth, frequent disconnections and lack of stable storage at mobile nodes. Previously proposed checkpoint algorithms for mobile environments do not take into consideration the coordinating message overhead of the mobile participants. In this paper, we propose a new checkpoint algorithm for mobile distributed systems. Our algorithm is nonblocking and minimizes the number of checkpoint participants. We propose a new idea called proxy coordinator. By using proxy coordinator, mobile participants' coordinating message overhead is minimized to O(1), which can otherwise be as high as O(n) in other proposed algorithms.

No abstract