Scalable Metadata Management Through OSD plus Devices
We present the design and implementation of both an enhanced new type of OSD device, the OSD+ device, and a metadata cluster based on it. The new OSD+ devices support data objects and directory objects. Unlike "data" objects, present in a traditional OSD, directory objects store file names and attributes, and support metadata-related operations. By using OSD+ devices, we show how the metadata cluster of the Fusion Parallel File System (FPFS) can effectively be managed by all the servers in a system, improving the performance, scalability and availability of the metadata service. We also describe how a directory with millions of files, and accessed by thousands of clients at the same time, is efficiently distributed across several servers to provide high IOPS rates. The performance of our metadata cluster based on OSD+s has been evaluated and compared with that achieved by Lustre. The results show that our proposal obtains a better throughput than Lustre when both use a single metadata server, easily getting improvements of more than 60-80%, and that the performance scales with the number of OSD+s. They also show that FPFS is able to provide a sustained throughput of more than 70,000 creates per second, and more than 120,000 stats per second, for huge directories on a cluster with just 8 OSD+s.
scalability osd metadata cluster fusion parallel file system management of huge directories