|
On 29.03.2018 10:25, ST Wong (ITSC)
wrote:
my guesstimate is that the serverroom with 3 mons will retain quorum, and continue operation. the room with 2 mon's will notice they are split out and block. assuming you have 3+2 pools and one of the objects is allways on the other server room. some pg's will be active becouse you have 2 objects on the working room. but some pg's will be inactive until they can selfheal and backfill a second copy of the objects. i assume you could have 4+2 replication to avoid this issue. ofcourse the 4 osd's left working now want to selfheal by recreating all objects stored on the 4 split off osd's and have a huge recovery job. and you may risk that the osd's goes into too_full error, unless you have free space in your osd's to recreate all the data in the defective part of the cluster. or they will be stuck in recovery mode until you get the second room running, this depends on your crush map. if you really need to split a cluster into separate rooms, i would have used 3 rooms, with redundant data paths between them. primary path between room A and C is direct. redundant path is via A-B-C. this should reduce the disaster if a single path is broken. with 1 mon in each room. you can loose a whole room to powerloss, and still have a working cluster. and you would only need 33% instead of 50% cluster capacity as free space in your cluster to be able to selfheal point in that slitting the cluster hurts. and if HA is the most important then you may want to check out rbd mirror. kind Ronny Aasen |
_______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
