Hi, I had to map a rbd from an ubuntu Trusty luminous client on an octopus cluster. client dmesg : feature set mismatch, my 4a042a42 < server's 100004a042a42, missing 1000000000000 I downgrade my osd tunable to bobtail but it still doesn't work ceph osd crush show-tunables { "choose_local_tries": 0, "choose_local_fallback_tries": 0, "choose_total_tries": 50, "chooseleaf_descend_once": 1, "chooseleaf_vary_r": 0, "chooseleaf_stable": 0, "straw_calc_version": 1, "allowed_bucket_algs": 22, "profile": "bobtail", "optimal_tunables": 0, "legacy_tunables": 0, "minimum_required_version": "hammer", "require_feature_tunables": 1, "require_feature_tunables2": 1, "has_v2_rules": 0, "require_feature_tunables3": 0, "has_v3_rules": 0, "has_v4_buckets": 1, "require_feature_tunables5": 0, "has_v5_rules": 0 } Thanks for your help. Marc