Configuring Monitor/OSD Interaction¶
After you have completed your initial Ceph configuration, you may deploy and run
Ceph. When you execute a command such as ceph health or ceph -s, the
Ceph Monitor reports on the current state of the Ceph Storage
Cluster. The Ceph Monitor knows about the Ceph Storage Cluster by requiring
reports from each Ceph OSD Daemon, and by receiving reports from Ceph
OSD Daemons about the status of their neighboring Ceph OSD Daemons. If the Ceph
Monitor doesn’t receive reports, or if it receives reports of changes in the
Ceph Storage Cluster, the Ceph Monitor updates the status of the Ceph
Cluster Map.
Ceph provides reasonable default settings for Ceph Monitor/Ceph OSD Daemon interaction. However, you may override the defaults. The following sections describe how Ceph Monitors and Ceph OSD Daemons interact for the purposes of monitoring the Ceph Storage Cluster.
OSDs Check Heartbeats¶
Each Ceph OSD Daemon checks the heartbeat of other Ceph OSD Daemons every 6
seconds. You can change the heartbeat interval by adding an osd heartbeat
interval setting under the [osd] section of your Ceph configuration file,
or by setting the value at runtime. If a neighboring Ceph OSD Daemon doesn’t
show a heartbeat within a 20 second grace period, the Ceph OSD Daemon may
consider the neighboring Ceph OSD Daemon down and report it back to a Ceph
Monitor, which will update the Ceph Cluster Map. You may change this grace
period by adding an osd heartbeat grace setting under the [mon]
and [osd] or [global] section of your Ceph configuration file,
or by setting the value at runtime.
OSDs Report Down OSDs¶
By default, two Ceph OSD Daemons from different hosts must report to the Ceph
Monitors that another Ceph OSD Daemon is down before the Ceph Monitors
acknowledge that the reported Ceph OSD Daemon is down. But there is chance
that all the OSDs reporting the failure are hosted in a rack with a bad switch
which has trouble connecting to another OSD. To avoid this sort of false alarm,
we consider the peers reporting a failure a proxy for a potential “subcluster”
over the overall cluster that is similarly laggy. This is clearly not true in
all cases, but will sometimes help us localize the grace correction to a subset
of the system that is unhappy. mon osd reporter subtree level is used to
group the peers into the “subcluster” by their common ancestor type in CRUSH
map. By default, only two reports from different subtree are required to report
another Ceph OSD Daemon down. You can change the number of reporters from
unique subtrees and the common ancestor type required to report a Ceph OSD
Daemon down to a Ceph Monitor by adding an mon osd min down reporters
and mon osd reporter subtree level settings under the [mon] section of
your Ceph configuration file, or by setting the value at runtime.
OSDs Report Peering Failure¶
If a Ceph OSD Daemon cannot peer with any of the Ceph OSD Daemons defined in its
Ceph configuration file (or the cluster map), it will ping a Ceph Monitor for
the most recent copy of the cluster map every 30 seconds. You can change the
Ceph Monitor heartbeat interval by adding an osd mon heartbeat interval
setting under the [osd] section of your Ceph configuration file, or by
setting the value at runtime.
OSDs Report Their Status¶
If an Ceph OSD Daemon doesn’t report to a Ceph Monitor, the Ceph Monitor will
consider the Ceph OSD Daemon down after the mon osd report timeout
elapses. A Ceph OSD Daemon sends a report to a Ceph Monitor when a reportable
event such as a failure, a change in placement group stats, a change in
up_thru or when it boots within 5 seconds. You can change the Ceph OSD
Daemon minimum report interval by adding an osd mon report interval min
setting under the [osd] section of your Ceph configuration file, or by
setting the value at runtime. A Ceph OSD Daemon sends a report to a Ceph
Monitor every 120 seconds irrespective of whether any notable changes occur.
You can change the Ceph Monitor report interval by adding an osd mon report
interval max setting under the [osd] section of your Ceph configuration
file, or by setting the value at runtime.
Configuration Settings¶
When modifying heartbeat settings, you should include them in the [global]
section of your configuration file.
Monitor Settings¶
mon osd min up ratio
| Description: | The minimum ratio of up Ceph OSD Daemons before Ceph will
mark Ceph OSD Daemons down. |
|---|---|
| Type: | Double |
| Default: | .3 |
mon osd min in ratio
| Description: | The minimum ratio of in Ceph OSD Daemons before Ceph will
mark Ceph OSD Daemons out. |
|---|---|
| Type: | Double |
| Default: | .75 |
mon osd laggy halflife
| Description: | The number of seconds laggy estimates will decay. |
|---|---|
| Type: | Integer |
| Default: | 60*60 |
mon osd laggy weight
| Description: | The weight for new samples in laggy estimation decay. |
|---|---|
| Type: | Double |
| Default: | 0.3 |
mon osd laggy max interval
| Description: | Maximum value of laggy_interval in laggy estimations (in seconds).
Monitor uses an adaptive approach to evaluate the laggy_interval of
a certain OSD. This value will be used to calculate the grace time for
that OSD. |
|---|---|
| Type: | Integer |
| Default: | 300 |
mon osd adjust heartbeat grace
| Description: | If set to true, Ceph will scale based on laggy estimations. |
|---|---|
| Type: | Boolean |
| Default: | true |
mon osd adjust down out interval
| Description: | If set to true, Ceph will scaled based on laggy estimations. |
|---|---|
| Type: | Boolean |
| Default: | true |
mon osd auto mark in
| Description: | Ceph will mark any booting Ceph OSD Daemons as in
the Ceph Storage Cluster. |
|---|---|
| Type: | Boolean |
| Default: | false |
mon osd auto mark auto out in
| Description: | Ceph will mark booting Ceph OSD Daemons auto marked out
of the Ceph Storage Cluster as in the cluster. |
|---|---|
| Type: | Boolean |
| Default: | true |
mon osd auto mark new in
| Description: | Ceph will mark booting new Ceph OSD Daemons as in the
Ceph Storage Cluster. |
|---|---|
| Type: | Boolean |
| Default: | true |
mon osd down out interval
| Description: | The number of seconds Ceph waits before marking a Ceph OSD Daemon
down and out if it doesn’t respond. |
|---|---|
| Type: | 32-bit Integer |
| Default: | 600 |
mon osd down out subtree limit
| Description: | The smallest CRUSH unit type that Ceph will not
automatically mark out. For instance, if set to host and if
all OSDs of a host are down, Ceph will not automatically mark out
these OSDs. |
|---|---|
| Type: | String |
| Default: | rack |
mon osd report timeout
| Description: | The grace period in seconds before declaring
unresponsive Ceph OSD Daemons down. |
|---|---|
| Type: | 32-bit Integer |
| Default: | 900 |
mon osd min down reporters
| Description: | The minimum number of Ceph OSD Daemons required to report a
down Ceph OSD Daemon. |
|---|---|
| Type: | 32-bit Integer |
| Default: | 2 |
mon osd reporter subtree level
| Description: | In which level of parent bucket the reporters are counted. The OSDs send failure reports to monitor if they find its peer is not responsive. And monitor mark the reported OSD out and then down after a grace period. |
|---|---|
| Type: | String |
| Default: | host |
OSD Settings¶
osd heartbeat address
| Description: | An Ceph OSD Daemon’s network address for heartbeats. |
|---|---|
| Type: | Address |
| Default: | The host address. |
osd heartbeat interval
| Description: | How often an Ceph OSD Daemon pings its peers (in seconds). |
|---|---|
| Type: | 32-bit Integer |
| Default: | 6 |
osd heartbeat grace
| Description: | The elapsed time when a Ceph OSD Daemon hasn’t shown a heartbeat
that the Ceph Storage Cluster considers it down.
This setting has to be set in both the [mon] and [osd] or [global]
section so that it is read by both the MON and OSD daemons. |
|---|---|
| Type: | 32-bit Integer |
| Default: | 20 |
osd mon heartbeat interval
| Description: | How often the Ceph OSD Daemon pings a Ceph Monitor if it has no Ceph OSD Daemon peers. |
|---|---|
| Type: | 32-bit Integer |
| Default: | 30 |
osd mon report interval max
| Description: | The maximum time in seconds that a Ceph OSD Daemon can wait before it must report to a Ceph Monitor. |
|---|---|
| Type: | 32-bit Integer |
| Default: | 120 |
osd mon report interval min
| Description: | The minimum number of seconds a Ceph OSD Daemon may wait from startup or another reportable event before reporting to a Ceph Monitor. |
|---|---|
| Type: | 32-bit Integer |
| Default: | 5 |
| Valid Range: | Should be less than osd mon report interval max |
osd mon ack timeout
| Description: | The number of seconds to wait for a Ceph Monitor to acknowledge a request for statistics. |
|---|---|
| Type: | 32-bit Integer |
| Default: | 30 |
