mirror of
https://github.com/ceph/ceph
synced 2024-12-23 11:54:11 +00:00
340 lines
12 KiB
ReStructuredText
340 lines
12 KiB
ReStructuredText
==============================
|
|
Recovering from OSD Failures
|
|
==============================
|
|
|
|
Single OSD Failure
|
|
==================
|
|
|
|
When a ``ceph-osd`` process dies, the monitor will learn about the failure
|
|
from surviving ``ceph-osd`` daemons and report it via the ``ceph health``
|
|
command::
|
|
|
|
ceph health
|
|
HEALTH_WARN 1/3 in osds are down
|
|
|
|
Specifically, you will get a warning whenever there are ``ceph-osd``
|
|
processes that are marked ``in`` and ``down``. You can identify which
|
|
``ceph-osds`` are ``down`` with::
|
|
|
|
ceph health detail
|
|
HEALTH_WARN 1/3 in osds are down
|
|
osd.0 is down since epoch 23, last address 192.168.106.220:6800/11080
|
|
|
|
Under normal circumstances, simply restarting the ``ceph-osd`` daemon will
|
|
allow it to rejoin the cluster and recover. If there is a disk
|
|
failure or other fault preventing ``ceph-osd`` from functioning or
|
|
restarting, an error message should be present in its log file in
|
|
``/var/log/ceph``.
|
|
|
|
If the daemon stopped because of a heartbeat failure, the underlying
|
|
kernel file system may be unresponsive. Check ``dmesg`` output for disk
|
|
or other kernel errors.
|
|
|
|
If the problem is a software error (failed assertion or other
|
|
unexpected error), it should be reported to the :ref:`mailing list
|
|
<mailing-list>`.
|
|
|
|
|
|
The Cluster Has No Free Disk Space
|
|
==================================
|
|
|
|
If the cluster fills up, the monitor will prevent new data from being
|
|
written. The system puts ``ceph-osds`` in two categories: ``nearfull``
|
|
and ``full``, with configurable threshholds for each (80% and 90% by
|
|
default). In both cases, full ``ceph-osds`` will be reported by ``ceph health``::
|
|
|
|
ceph health
|
|
HEALTH_WARN 1 nearfull osds
|
|
osd.2 is near full at 85%
|
|
|
|
Or::
|
|
|
|
ceph health
|
|
HEALTH_ERR 1 nearfull osds, 1 full osds
|
|
osd.2 is near full at 85%
|
|
osd.3 is full at 97%
|
|
|
|
The best way to deal with a full cluster is to add new ``ceph-osds``,
|
|
allowing the cluster to redistribute data to the newly available
|
|
storage.
|
|
|
|
|
|
Homeless Placement Groups
|
|
=========================
|
|
|
|
It is possible for all OSDs that had copies of a given placement groups to fail.
|
|
If that's the case, that subset of the object store is unavailable, and the
|
|
monitor will receive no status updates for those placement groups. To detect
|
|
this situation, the monitor marks any placement group whose primary OSD has
|
|
failed as ``stale``. For example::
|
|
|
|
ceph health
|
|
HEALTH_WARN 24 pgs stale; 3/300 in osds are down
|
|
|
|
You can identify which placement groups are ``stale``, and what the last OSDs to
|
|
store them were, with::
|
|
|
|
ceph health detail
|
|
HEALTH_WARN 24 pgs stale; 3/300 in osds are down
|
|
...
|
|
pg 2.5 is stuck stale+active+remapped, last acting [2,0]
|
|
...
|
|
osd.10 is down since epoch 23, last address 192.168.106.220:6800/11080
|
|
osd.11 is down since epoch 13, last address 192.168.106.220:6803/11539
|
|
osd.12 is down since epoch 24, last address 192.168.106.220:6806/11861
|
|
|
|
If we want to get placement group 2.5 back online, for example, this tells us that
|
|
it was last managed by ``osd.0`` and ``osd.2``. Restarting those ``ceph-osd``
|
|
daemons will allow the cluster to recover that placement group (and, presumably,
|
|
many others).
|
|
|
|
|
|
Stuck Placement Groups
|
|
======================
|
|
|
|
It is normal for placement groups to enter states like "degraded" or "peering"
|
|
following a failure. Normally these states indicate the normal progression
|
|
through the failure recovery process. However, if a placement group stays in one
|
|
of these states for a long time this may be an indication of a larger problem.
|
|
For this reason, the monitor will warn when placement groups get "stuck" in a
|
|
non-optimal state. Specifically, we check for:
|
|
|
|
* ``inactive`` - The placement group has not been ``active`` for too long
|
|
(i.e., it hasn't been able to service read/write requests).
|
|
|
|
* ``unclean`` - The placement group has not been ``clean`` for too long
|
|
(i.e., it hasn't been able to completely recover from a previous failure).
|
|
|
|
* ``stale`` - The placement group status has not been updated by a ``ceph-osd``,
|
|
indicating that all nodes storing this placement group may be ``down``.
|
|
|
|
You can explicitly list stuck placement groups with one of::
|
|
|
|
ceph pg dump_stuck stale
|
|
ceph pg dump_stuck inactive
|
|
ceph pg dump_stuck unclean
|
|
|
|
For stuck ``stale`` placement groups, it is normally a matter of getting the
|
|
right ``ceph-osd`` daemons running again. For stuck ``inactive`` placement
|
|
groups, it is usually a peering problem (see :ref:`failures-osd-peering`). For
|
|
stuck ``unclean`` placement groups, there is usually something preventing
|
|
recovery from completing, like unfound objects (see
|
|
:ref:`failures-osd-unfound`);
|
|
|
|
|
|
.. _failures-osd-peering:
|
|
|
|
Placement Group Down - Peering Failure
|
|
======================================
|
|
|
|
In certain cases, the ``ceph-osd`` `Peering` process can run into
|
|
problems, preventing a PG from becoming active and usable. For
|
|
example, ``ceph health`` might report::
|
|
|
|
ceph health detail
|
|
HEALTH_ERR 7 pgs degraded; 12 pgs down; 12 pgs peering; 1 pgs recovering; 6 pgs stuck unclean; 114/3300 degraded (3.455%); 1/3 in osds are down
|
|
...
|
|
pg 0.5 is down+peering
|
|
pg 1.4 is down+peering
|
|
...
|
|
osd.1 is down since epoch 69, last address 192.168.106.220:6801/8651
|
|
|
|
We can query the cluster to determine exactly why the PG is marked ``down`` with::
|
|
|
|
ceph pg 0.5 query
|
|
|
|
.. code-block:: javascript
|
|
|
|
{ "state": "down+peering",
|
|
...
|
|
"recovery_state": [
|
|
{ "name": "Started\/Primary\/Peering\/GetInfo",
|
|
"enter_time": "2012-03-06 14:40:16.169679",
|
|
"requested_info_from": []},
|
|
{ "name": "Started\/Primary\/Peering",
|
|
"enter_time": "2012-03-06 14:40:16.169659",
|
|
"probing_osds": [
|
|
0,
|
|
1],
|
|
"blocked": "peering is blocked due to down osds",
|
|
"down_osds_we_would_probe": [
|
|
1],
|
|
"peering_blocked_by": [
|
|
{ "osd": 1,
|
|
"current_lost_at": 0,
|
|
"comment": "starting or marking this osd lost may let us proceed"}]},
|
|
{ "name": "Started",
|
|
"enter_time": "2012-03-06 14:40:16.169513"}
|
|
]
|
|
}
|
|
|
|
The ``recovery_state`` section tells us that peering is blocked due to
|
|
down ``ceph-osd`` daemons, specifically ``osd.1``. In this case, we can start that ``ceph-osd``
|
|
and things will recover.
|
|
|
|
Alternatively, if there is a catastrophic failure of ``osd.1`` (e.g., disk
|
|
failure), we can tell the cluster that it is ``lost`` and to cope as
|
|
best it can.
|
|
|
|
.. important:: This is dangerous in that the cluster cannot
|
|
guarantee that the other copies of the data are consistent
|
|
and up to date.
|
|
|
|
To instruct Ceph to continue anyway::
|
|
|
|
ceph osd lost 1
|
|
|
|
Recovery will proceed.
|
|
|
|
|
|
.. _failures-osd-unfound:
|
|
|
|
Unfound Objects
|
|
===============
|
|
|
|
Under certain combinations of failures Ceph may complain about
|
|
``unfound`` objects::
|
|
|
|
ceph health detail
|
|
HEALTH_WARN 1 pgs degraded; 78/3778 unfound (2.065%)
|
|
pg 2.4 is active+degraded, 78 unfound
|
|
|
|
This means that the storage cluster knows that some objects (or newer
|
|
copies of existing objects) exist, but it hasn't found copies of them.
|
|
One example of how this might come about for a PG whose data is on ceph-osds
|
|
1 and 2:
|
|
|
|
* 1 goes down
|
|
* 2 handles some writes, alone
|
|
* 1 comes up
|
|
* 1 and 2 repeer, and the objects missing on 1 are queued for recovery.
|
|
* Before the new objects are copied, 2 goes down.
|
|
|
|
Now 1 knows that these object exist, but there is no live ``ceph-osd`` who
|
|
has a copy. In this case, IO to those objects will block, and the
|
|
cluster will hope that the failed node comes back soon; this is
|
|
assumed to be preferable to returning an IO error to the user.
|
|
|
|
First, you can identify which objects are unfound with::
|
|
|
|
ceph pg 2.4 list_missing [starting offset, in json]
|
|
|
|
.. code-block:: javascript
|
|
|
|
{ "offset": { "oid": "",
|
|
"key": "",
|
|
"snapid": 0,
|
|
"hash": 0,
|
|
"max": 0},
|
|
"num_missing": 0,
|
|
"num_unfound": 0,
|
|
"objects": [
|
|
{ "oid": "object 1",
|
|
"key": "",
|
|
"hash": 0,
|
|
"max": 0 },
|
|
...
|
|
],
|
|
"more": 0}
|
|
|
|
If there are too many objects to list in a single result, the ``more``
|
|
field will be true and you can query for more. (Eventually the
|
|
command line tool will hide this from you, but not yet.)
|
|
|
|
Second, you can identify which OSDs have been probed or might contain
|
|
data::
|
|
|
|
ceph pg 2.4 query
|
|
|
|
.. code-block:: javascript
|
|
|
|
"recovery_state": [
|
|
{ "name": "Started\/Primary\/Active",
|
|
"enter_time": "2012-03-06 15:15:46.713212",
|
|
"might_have_unfound": [
|
|
{ "osd": 1,
|
|
"status": "osd is down"}]},
|
|
|
|
In this case, for example, the cluster knows that ``osd.1`` might have
|
|
data, but it is ``down``. The full range of possible states include::
|
|
|
|
* already probed
|
|
* querying
|
|
* osd is down
|
|
* not queried (yet)
|
|
|
|
Sometimes it simply takes some time for the cluster to query possible
|
|
locations.
|
|
|
|
It is possible that there are other locations where the object can
|
|
exist that are not listed. For example, if a ceph-osd is stopped and
|
|
taken out of the cluster, the cluster fully recovers, and due to some
|
|
future set of failures ends up with an unfound object, it won't
|
|
consider the long-departed ceph-osd as a potential location to
|
|
consider. (This scenario, however, is unlikely.)
|
|
|
|
If all possible locations have been queried and objects are still
|
|
lost, you may have to give up on the lost objects. This, again, is
|
|
possible given unusual combinations of failures that allow the cluster
|
|
to learn about writes that were performed before the writes themselves
|
|
are recovered. To mark the "unfound" objects as "lost"::
|
|
|
|
ceph pg 2.5 mark_unfound_lost revert
|
|
|
|
This the final argument specifies how the cluster should deal with
|
|
lost objects. Currently the only supported option is "revert", which
|
|
will either roll back to a previous version of the object or (if it
|
|
was a new object) forget about it entirely. Use this with caution, as
|
|
it may confuse applications that expected the object to exist.
|
|
|
|
|
|
|
|
Slow or Unresponsive OSD
|
|
========================
|
|
|
|
If, for some reason, a ``ceph-osd`` is slow to respond to a request, it will
|
|
generate log messages complaining about requests that are taking too
|
|
long. The warning threshold defaults to 30 seconds, and is configurable
|
|
via the ``osd op complaint time`` option. When this happens, the cluster
|
|
log will receive messages like::
|
|
|
|
osd.0 192.168.106.220:6800/18813 312 : [WRN] old request osd_op(client.5099.0:790 fatty_26485_object789 [write 0~4096] 2.5e54f643) v4 received at 2012-03-06 15:42:56.054801 currently waiting for sub ops
|
|
|
|
Possible causes include:
|
|
|
|
* bad disk (check ``dmesg`` output)
|
|
* kernel file system bug (check ``dmesg`` output)
|
|
* overloaded cluster (check system load, iostat, etc.)
|
|
* ceph-osd bug
|
|
|
|
|
|
Flapping OSDs
|
|
=============
|
|
|
|
If something is causing OSDs to "flap" (repeatedly getting marked ``down`` and then
|
|
``up`` again), you can force the monitors to stop with::
|
|
|
|
ceph osd set noup # prevent osds from getting marked up
|
|
ceph osd set nodown # prevent osds from getting marked down
|
|
|
|
These flags are recorded in the osdmap structure::
|
|
|
|
ceph osd dump | grep flags
|
|
flags no-up,no-down
|
|
|
|
You can clear the flags with::
|
|
|
|
ceph osd unset noup
|
|
ceph osd unset nodown
|
|
|
|
Two other flags are supported, ``noin`` and ``noout``, which prevent
|
|
booting OSDs from being marked ``in`` (allocated data) or down
|
|
ceph-osds from eventually being marked ``out`` (regardless of what the
|
|
current value for ``mon osd down out interval`` is).
|
|
|
|
Note that ``noup``, ``noout``, and ``noout`` are temporary in the
|
|
sense that once the flags are cleared, the action they were blocking
|
|
should occur shortly after. The ``noin`` flag, on the other hand,
|
|
prevents ceph-osds from being marked in on boot, and any daemons that
|
|
started while the flag was set will remain that way.
|