Hi, On Mon, 2011-07-04 at 20:17 +0300, Vasilakakos Giorgos wrote: > Hello folks, I have a question: > I know files get mapped to objects and those objects to OSDs but how > exactly do we go from one to the other? > What I mean is, given the filename I want to access how does Ceph find > the relevant objects? What exactly does CRUSH do? > Supposedly, the client first asks the MDS for an inode number, what then? > How are the object and PG IDs constructed and where exactly does CRUSH come in? > My impression is that the OID is made from the name, inode and > probably some kind of information about the striping of the file, > what about the mapping of an object to a PG? > Are PGs mapped to OSDs by means of CRUSH, or are objects mapped to PGs > by CRUSH? How are PGs assigned to OSDs then? > > Could someone clarify this part for me? Have you read the RADOS, CRUSH and Ceph thesis on the website? Try: * http://ceph.newdream.net/weil-thesis.pdf * http://ceph.newdream.net/papers/weil-rados-pdsw07.pdf * http://ceph.newdream.net/papers/weil-ceph-osdi06.pdf * http://ceph.newdream.net/papers/weil-crush-sc06.pdf I think that should cover most of it. > > Thanks in advance > -- > 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
