REC2: Restoration Method Using Combination of Replication and Erasure Coding

When large-scale disasters occur, such as the Great East Earthquake Japan occurred in March 2011, servers located in the affected area are sometimes disrupted. If the servers has important information, such as medical information, it is crucial to restore the servers because the information is utilized by medical activities. Therefore, the servers must be restored as soon as possible. We propose a restoration method using the combination of replication method and erasure coding method, called REstoration method using Combination of Replication and Erasure Coding (REC2.) REC2 applies the replication method to the meta-data of a file, and it also applies the erasure coding method to the user-data of the file. The combination achieves the both the high restoration throughput with the amount of the backup data reduced. In this paper, we describe the implementation details of REC2 and evaluation results. In the evaluation, we compare REC2 with the conventional restoration method about the amount of backup data and the restoration throughput. From the results, we found out that REC2 provides higher restoration throughput than the conventional restoration method while REC2 reduces the amount of backup data.