Hi, everyone. After a year of cephfs experience, we find QoS, especially metadata operation QoS, an inevitable requirement for the large-scale application of CephFS as we don't wan't a small number of clients to use up all MDS resources. Since the MDS doesn't have a QoS support for now, we think maybe we can implement some kind of client-side throttling of metadata operations which should meet our requirements mentioned above and be easy to implement. We plan to implement such a mechanism as part of the current Quota mechanism to give users the ability to limit, in addition to the file number or disk space usage, how many metadata operations can be done per second for a single client under a specific directory. Is this the right way to go? And, after the implementation of this client-side throttling, we might, as well, seek to find a way to do the real metadata operation QoS, is dmclock a good algorithm for file system metadata op QoS? Thanks for very mych:-)
