Hi, On Tue, 2011-07-05 at 00:25 +0800, Fusheng Han wrote: > Hi, all > > After reading the RADOS paper, I have some questions about > availability of RADOS. Nowhere I can find to discuss, so I'm here. > When adding new host to the cluster, some placement group will be > mapped to the new one. After the cluster info incremental propagates > to all the OSDs and clients, the client write operation will be > directed to the PG whose primary is at the new host. Before the new > host get the data migration down, it can not service these requests. > And due to the limitation of network bandwidth, the data migration may > take long. There is a long time that the new host can not service. I > got confused. Yes, during migration a PG will become unavailable for a short period of time. In a large cluster you have a large number of PGs where each PG doesn't contain that much data, which makes this period short. What kind of bandwith are you talking about? Ceph/RADOS is intended to run in datacenters where you have low latency high bandwith (1G) networks. Migrating a PG would take that much time in such environments. Wido > Do I miss something important in this paper? > > Thank you all > Fusheng Han > -- > 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 -- 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
