File placement mechanisms for improving write throughputs of cloud storage services based on Ceph and HDFS

Cloud storage services are pervasive nowadays. Many cloud storage services use distributed file systems as their backend storage systems. Some research results on file-size distribution of file systems show that file systems contain lots of small files. Therefore, this paper proposed a hybrid distributed file system based on Ceph and HDFS that can deliver satisfactory write throughputs for a cloud storage system with 80-90% small files and 10-20% large files. The experimental results show that the file allocation mechanism without RAM disk caching can improve the write throughputs of Ceph and HDFS by approximately 10% to 50%. While the one with RAM disk caching can have up to 200% write throughputs improvement.