From: Jonas Jelten Date: Sun, 20 Sep 2020 21:05:33 +0000 (+0200) Subject: doc: fix and improve the explainations of up and acting osd sets X-Git-Tag: v16.1.0~162^2 X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=refs%2Fpull%2F37267%2Fhead;p=ceph.git doc: fix and improve the explainations of up and acting osd sets acting = where clients requests are processed up = where pgs were planned to be by crush+upmap Fixes: https://tracker.ceph.com/issues/48718 Signed-off-by: Jonas Jelten --- diff --git a/doc/rados/operations/monitoring-osd-pg.rst b/doc/rados/operations/monitoring-osd-pg.rst index 08b70dd4d51c..86b85e7b48d5 100644 --- a/doc/rados/operations/monitoring-osd-pg.rst +++ b/doc/rados/operations/monitoring-osd-pg.rst @@ -109,9 +109,15 @@ requires three replicas of a placement group, CRUSH may assign them to ``osd.1``, ``osd.2`` and ``osd.3`` respectively. CRUSH actually seeks a pseudo-random placement that will take into account failure domains you set in your `CRUSH map`_, so you will rarely see placement groups assigned to nearest -neighbor OSDs in a large cluster. We refer to the set of OSDs that should -contain the replicas of a particular placement group as the **Acting Set**. In -some cases, an OSD in the Acting Set is ``down`` or otherwise not able to +neighbor OSDs in a large cluster. + +Ceph processes a client request using the **Acting Set**, which is the set of +OSDs that will actually handle the requests since they have a full and working +version of a placement group shard. The set of OSDs that should contain a shard +of a particular placement group as the **Up Set**, i.e. where data is +moved/copied to (or planned to be). + +In some cases, an OSD in the Acting Set is ``down`` or otherwise not able to service requests for objects in the placement group. When these situations arise, don't panic. Common examples include: @@ -122,12 +128,10 @@ arise, don't panic. Common examples include: - An OSD in the Acting Set is ``down`` or unable to service requests, and another OSD has temporarily assumed its duties. -Ceph processes a client request using the **Up Set**, which is the set of OSDs -that will actually handle the requests. In most cases, the Up Set and the Acting -Set are virtually identical. When they are not, it may indicate that Ceph is -migrating data, an OSD is recovering, or that there is a problem (i.e., Ceph -usually echoes a "HEALTH WARN" state with a "stuck stale" message in such -scenarios). +In most cases, the Up Set and the Acting Set are identical. When they are not, +it may indicate that Ceph is migrating the PG (it's remapped), an OSD is +recovering, or that there is a problem (i.e., Ceph usually echoes a "HEALTH +WARN" state with a "stuck stale" message in such scenarios). To retrieve a list of placement groups, execute::