I wanted to share some of the initial performance results of CephFS using single and multiple MDS. These results are currently hosted here: https://github.com/batrick/cephfs-perf It has been some time since we've done an analysis of MDS performance (especially multiple active MDS). One of the goals of this study is to obtain performance metrics which confirm multiple active metadata servers (multimds) function in ways we expect. We are also looking to establish a base-line performance for a single active metadata server, such as how many concurrent clients one MDS can handle. The first experiment [3] is evaluating the performance of one and three active metadata servers against parallel kernel builds by clients (8 and 16). This is a situation we would expect multiple metadata servers to excel at with dynamic sub-tree partitioning [1,2]. Additionally, because clients operate in independent trees, lock contention and forced journal flushes should be mostly eliminated. While there is still performance data to analyze, the initial results indicate multimds can give impressive performance gains, especially as the number of clients increase. For example, with 16 clients we saw improvements of 74% in execution time of the clients and an 84% reduction in client request latency (time spent by the client waiting for a result from the MDS). Future tests are being planned. If anyone has comments/questions/suggestions, please do share. [1] http://dl.acm.org/citation.cfm?id=1049948 [2] http://ceph.com/papers/weil-mds-sc04.pdf [3] https://github.com/batrick/cephfs-perf/tree/master/kernel-build -- Patrick Donnelly -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
