That was clearly explained. Thank you so much! Best regards, Cody On Sat, Oct 20, 2018 at 1:02 PM Maged Mokhtar <mmokhtar@xxxxxxxxxxx> wrote: > > > > On 20/10/18 05:28, Cody wrote: > > Hi folks, > > > > I have a rookie question. Does the number of the buckets chosen as the > > failure domain must be equal or greater than the number of replica (or > > k+m for erasure coding)? > > > > E.g., for an erasure code profile where k=4, m=2, failure domain=rack, > > does it only work when there are 6 or more racks in the CRUSH > > hierarchy? Or would it continue to iterate down the tree and > > eventually would work as long as there are 6 or more OSDs? > > > > Thank you very much. > > > > Best regards, > > Cody > > _______________________________________________ > > ceph-users mailing list > > ceph-users@xxxxxxxxxxxxxx > > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > The rule associated with the ec profile you mentioned, will indeed try > to select 6 rack buckets then get an osd leaf from each. If you only had > 5 racks for example, it will return only 5 osds per PG, the pool will > function but in degraded state (if pool min_size was 5). This rule will > not return more that 1 osd per rack, if it did it will not achieving the > failure domain you gave. > You can write a custom rule that uses 2 racks and select 3 hosts from > each, and associate this with the k4 m2 pool, crush will not mind..it > will do whatever you tell it, but if 1 rack fails your pool goes down, > so would not be achieving a failure domain at rack level unless you do > have 6 or more racks. > > Maged > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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