There's not really a simple way to do this. There are functions in the OSDMap structure to calculate the location of a particular PG, but there are a lot of independent places that map objects into PGs.
On Monday, June 23, 2014, Shayan Saeed <shayansaee...@gmail.com> wrote: > Thanks for getting back with a helpful reply. Assuming that I change the > source code to do custom placement, what are the places I need to look in > the code to do that? I am currently trying to change the CRUSH code, but is > there any place else I need to be concerned about? > > Regards, > Shayan Saeed > > > On Mon, Jun 23, 2014 at 2:14 PM, Gregory Farnum <g...@inktank.com > <javascript:_e(%7B%7D,'cvml','g...@inktank.com');>> wrote: > >> On Fri, Jun 20, 2014 at 4:23 PM, Shayan Saeed <shayansaee...@gmail.com >> <javascript:_e(%7B%7D,'cvml','shayansaee...@gmail.com');>> wrote: >> > Is it allowed for crush maps to have multiple hierarchies for different >> > pools. So for example, I want one pool to treat my cluster as flat with >> > every host being equal but the other pool to have a more hierarchical >> idea >> > as hosts->racks->root? >> >> Yes. It can get complicated, so make sure you know exactly what you're >> doing, but you can create different "root" buckets and link the OSDs >> in to each root in different ways. >> >> > >> > Also, is it currently possible in ceph to have a custom placement of >> erasure >> > coded chunks. So for example within a pool, I want objects to reside >> exactly >> > on the OSDs I choose instead of doing placement for load balancing. Can >> I >> > specify something like: "For object 1, I want systematic chunks on >> rack1 and >> > non systematic distributed between rack2 and rack3 and then for object >> 2, I >> > want systematic ones on rack2 and non systematic distributed between >> rack1 >> > and rack3"? >> >> Not generally, no — you need to let the CRUSH algorithm place them. >> You can do things like specify specific buckets within a CRUSH rule, >> but that applies on a pool level. >> -Greg >> Software Engineer #42 @ http://inktank.com | http://ceph.com >> >> > >> > I would greatly appreciate any suggestions I get. >> > >> > Regards, >> > Shayan Saeed >> > >> > _______________________________________________ >> > ceph-users mailing list >> > ceph-users@lists.ceph.com >> <javascript:_e(%7B%7D,'cvml','ceph-users@lists.ceph.com');> >> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >> > >> > > -- Software Engineer #42 @ http://inktank.com | http://ceph.com
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