On 05/23/2015 08:58 AM, 李沛伦 wrote: > Hello! > > I'm a GSoC student this year and my job is to introduce Missing Rate > Curve (or reuse distance exactly) of objects into OSD. Now I'm trying > to find a proper algorithm to implement but there is a problem: Should > I take the number of objects tracked in an OSD as infinite or > constant? > A OSD doesn't track on a per-object basis, but it keeps track of Placement Groups (PGs). A OSD can have a X number of PGs. Technically the number of PGs might be infinite, but in practice you are bound to CPU and Memory limits. So I would be careful with the word "infinite", since nothing is really infinite, eg size of a int/long might be the limitation for something. But in theory there is no object or PG limit per OSD. > The point is that there is an algorithm that use hash to sample only > constant number of references to do the analysis and is proved to be > accurate, which makes it possible to do online MRC construction. That > accuracy is supported by the fact that the memory addresses is > bounded, while objects can be deleted and created again and again in > Ceph. Is is reasonable to think that an OSD only serves bounded number > of objects in its life time (or the time period that we want to > compute MRC)? > > Any other comment about this project is also welcomed :) > -- Wido den Hollander 42on B.V. Ceph trainer and consultant Phone: +31 (0)20 700 9902 Skype: contact42on -- 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
