From: Anthony D'Atri <anthonyeleven@users.noreply.github.com>
Date: Fri, 7 Feb 2025 15:08:38 +0000 (-0500)
Subject: doc: Clarify that there are no tertiary OSDs
X-Git-Tag: v19.2.3~373^2
X-Git-Url: http://git.apps.os.sepia.ceph.com/?a=commitdiff_plain;h=695eb9937af1a941c30834b841ef026f03e91aeb;p=ceph.git

doc: Clarify that there are no tertiary OSDs

Signed-off-by: Anthony D'Atri <anthonyeleven@users.noreply.github.com>
(cherry picked from commit e261155a8a0234897803d38e899d10ec89b2b08f)
---

diff --git a/doc/architecture.rst b/doc/architecture.rst
index bf11cc3a6d2c4..8fd8aeeb98e69 100644
--- a/doc/architecture.rst
+++ b/doc/architecture.rst
@@ -437,7 +437,7 @@ the greater cluster provides several benefits:
    bad sectors on drives that are not detectable with light scrubs. See `Data
    Scrubbing`_ for details on configuring scrubbing.
 
-#. **Replication:** Data replication involves a collaboration between Ceph
+#. **Replication:** Data replication involves collaboration between Ceph
    Clients and Ceph OSD Daemons. Ceph OSD Daemons use the CRUSH algorithm to
    determine the storage location of object replicas. Ceph clients use the
    CRUSH algorithm to determine the storage location of an object, then the
@@ -446,11 +446,11 @@ the greater cluster provides several benefits:
 
    After identifying the target placement group, the client writes the object
    to the identified placement group's primary OSD. The primary OSD then
-   consults its own copy of the CRUSH map to identify secondary and tertiary
-   OSDS, replicates the object to the placement groups in those secondary and
-   tertiary OSDs, confirms that the object was stored successfully in the
-   secondary and tertiary OSDs, and reports to the client that the object
-   was stored successfully.
+   consults its own copy of the CRUSH map to identify secondary
+   OSDS, replicates the object to the placement groups in those secondary
+   OSDs, confirms that the object was stored successfully in the
+   secondary OSDs, and reports to the client that the object
+   was stored successfully.  We call these replication operations ``subops``.
 
 .. ditaa::
 
@@ -472,13 +472,13 @@ the greater cluster provides several benefits:
        |  +------+   +------+  |
        |  | Ack (4)  Ack (5)|  |
        v  *                 *  v
- +---------------+   +---------------+
- | Secondary OSD |   | Tertiary OSD  |
- |               |   |               |
- +---------------+   +---------------+
+ +---------------+   +----------------+
+ | Secondary OSD |   | Secondary OSD  |
+ |               |   |                |
+ +---------------+   +----------------+
 
-By performing this act of data replication, Ceph OSD Daemons relieve Ceph
-clients of the burden of replicating data.
+By performing this data replication, Ceph OSD Daemons relieve Ceph
+clients and their network interfaces of the burden of replicating data.
 
 Dynamic Cluster Management
 --------------------------
diff --git a/doc/rados/operations/pools.rst b/doc/rados/operations/pools.rst
index 9da4825099bde..2446aca558cb4 100644
--- a/doc/rados/operations/pools.rst
+++ b/doc/rados/operations/pools.rst
@@ -7,10 +7,11 @@ Pools are logical partitions that are used to store objects.
 
 Pools provide:
 
-- **Resilience**: It is possible to set the number of OSDs that are allowed to
-  fail without any data being lost. If your cluster uses replicated pools, the
-  number of OSDs that can fail without data loss is equal to the number of
-  replicas.
+- **Resilience**: It is possible to plan for the number of OSDs that may
+  fail in parallel without data being unavailable or lost. If your cluster
+  uses replicated pools, the number of OSDs that can fail in parallel without
+  data loss is one less than the number of replicas, and the number that can
+  fail without data becoming unavailable is usually two.
   
   For example: a typical configuration stores an object and two replicas
   (copies) of each RADOS object (that is: ``size = 3``), but you can configure
@@ -229,8 +230,8 @@ pool by running the following command.:
 Setting Pool Quotas
 ===================
 
-To set pool quotas for the maximum number of bytes and/or the maximum number of
-RADOS objects per pool, run the following command:
+To set quotas for the maximum number of bytes or the maximum number of
+RADOS objects per pool, run a command of the following form:
 
 .. prompt:: bash $
 
@@ -242,7 +243,8 @@ For example:
 
    ceph osd pool set-quota data max_objects 10000
 
-To remove a quota, set its value to ``0``.
+To remove a quota, set its value to ``0``.  Note that you may set a quota only
+for bytes or only for RADOS objects, or you can set both.
 
 
 Deleting a Pool