On Mon, Jul 10, 2017 at 7:44 AM, TYLin <wooertim@xxxxxxxxx> wrote:
> Hi all,
>
> We have a cluster whose fsmap and mdsmap have different value. Also, each mds has different mdsmap epoch. Active mds has epoch 52, and other two standby mds have 53 and 55, respectively. Why are the mdsmap epoch of each mds different?
This is normal. The epoch for each standby and each mdsmap indicates
the FSMap epoch where that thing was last updated. Every time we
change something, we increment the FSMap epoch, and then copy that
number into the epoch field of whichever part of the fsmap was
changed.
We do it this way so that if an MDS or client is subscribing to
updates for just an MDSMap (not the whole FSMap), then they only get
updates when something in that part changes, not when anything in the
FSMap changes. So the epoch number for an MDSMap will always
increase, but it will not be a contiguous range of numbers.
John
>
> Our cluster:
> ceph 11.2.0
> 3 nodes. Each node has a mon, mds and 4 OSDs.
>
> $ ceph mds stat --format=json
> {
> "fsmap": {
> "epoch": 55,
> "compat": {
> "compat": {},
> "ro_compat": {},
> "incompat": {
> "feature_1": "base v0.20",
> "feature_2": "client writeable ranges",
> "feature_3": "default file layouts on dirs",
> "feature_4": "dir inode in separate object",
> "feature_5": "mds uses versioned encoding",
> "feature_6": "dirfrag is stored in omap",
> "feature_8": "file layout v2"
> }
> },
> "feature_flags": {
> "enable_multiple": false,
> "ever_enabled_multiple": false
> },
> "standbys": [
> {
> "gid": 414444,
> "name": "Host2",
> "rank": -1,
> "incarnation": 0,
> "state": "up:standby",
> "state_seq": 2,
> "addr": "10.4.154.141:6816/304221716",
> "standby_for_rank": -1,
> "standby_for_fscid": -1,
> "standby_for_name": "",
> "standby_replay": false,
> "export_targets": [],
> "features": 1152921504336314400,
> "epoch": 53
> },
> {
> "gid": 424717,
> "name": "Host3",
> "rank": -1,
> "incarnation": 0,
> "state": "up:standby",
> "state_seq": 2,
> "addr": "10.4.154.142:6816/627678162",
> "standby_for_rank": -1,
> "standby_for_fscid": -1,
> "standby_for_name": "",
> "standby_replay": false,
> "export_targets": [],
> "features": 1152921504336314400,
> "epoch": 55
> }
> ],
> "filesystems": [
> {
> "mdsmap": {
> "epoch": 52,
> "flags": 0,
> "ever_allowed_features": 0,
> "explicitly_allowed_features": 0,
> "created": "2017-06-15 11:56:32.709015",
> "modified": "2017-06-15 11:56:32.709015",
> "tableserver": 0,
> "root": 0,
> "session_timeout": 60,
> "session_autoclose": 300,
> "max_file_size": 1099511627776,
> "last_failure": 0,
> "last_failure_osd_epoch": 154,
> "compat": {
> "compat": {},
> "ro_compat": {},
> "incompat": {
> "feature_1": "base v0.20",
> "feature_2": "client writeable ranges",
> "feature_3": "default file layouts on dirs",
> "feature_4": "dir inode in separate object",
> "feature_5": "mds uses versioned encoding",
> "feature_6": "dirfrag is stored in omap",
> "feature_8": "file layout v2"
> }
> },
> "max_mds": 1,
> "in": [
> 0
> ],
> "up": {
> "mds_0": 399818
> },
> "failed": [],
> "damaged": [],
> "stopped": [],
> "info": {
> "gid_399818": {
> "gid": 399818,
> "name": “Host1",
> "rank": 0,
> "incarnation": 49,
> "state": "up:active",
> "state_seq": 492,
> "addr": "10.4.154.140:6816/3168307953",
> "standby_for_rank": -1,
> "standby_for_fscid": -1,
> "standby_for_name": "",
> "standby_replay": false,
> "export_targets": [],
> "features": 1152921504336314400
> }
> },
> "data_pools": [
> 2
> ],
> "metadata_pool": 3,
> "enabled": true,
> "fs_name": "cephfs",
> "balancer": ""
> },
> "id": 1
> }
> ]
> },
> "mdsmap_first_committed": 1,
> "mdsmap_last_committed": 55
> }
>
> Thanks,
> Tim Lin
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