From 49efd1fc2f281801c4ef4ed2862e2409dff43b3a Mon Sep 17 00:00:00 2001 From: Zac Dover Date: Tue, 12 Sep 2023 21:17:40 +1000 Subject: [PATCH] doc/architecture: edit "Cluster Map" Edit the section "Cluster Map" in doc/architecture.rst. Co-authored-by: Anthony D'Atri Signed-off-by: Zac Dover (cherry picked from commit cc8dce2531e8fac64345c4b85087f52149e9a9d0) --- doc/architecture.rst | 53 ++++++++++++++++++++++++-------------------- 1 file changed, 29 insertions(+), 24 deletions(-) diff --git a/doc/architecture.rst b/doc/architecture.rst index dd0bdd2194eb4..4052a19bd6666 100644 --- a/doc/architecture.rst +++ b/doc/architecture.rst @@ -134,40 +134,45 @@ Decentralized Placement of Replicated Data`_. Cluster Map ~~~~~~~~~~~ -Ceph depends upon Ceph Clients and Ceph OSD Daemons having knowledge of the -cluster topology, which is inclusive of 5 maps collectively referred to as the -"Cluster Map": - -#. **The Monitor Map:** Contains the cluster ``fsid``, the position, name - address and port of each monitor. It also indicates the current epoch, - when the map was created, and the last time it changed. To view a monitor - map, execute ``ceph mon dump``. +In order for a Ceph cluster to function properly, Ceph Clients and Ceph OSDs +must have current information about the cluster's topology. Current information +is stored in the "Cluster Map", which is in fact a collection of five maps. The +five maps that constitute the cluster map are: + +#. **The Monitor Map:** Contains the cluster ``fsid``, the position, the name, + the address, and the TCP port of each monitor. The monitor map specifies the + current epoch, the time of the monitor map's creation, and the time of the + monitor map's last modification. To view a monitor map, run ``ceph mon + dump``. -#. **The OSD Map:** Contains the cluster ``fsid``, when the map was created and - last modified, a list of pools, replica sizes, PG numbers, a list of OSDs - and their status (e.g., ``up``, ``in``). To view an OSD map, execute - ``ceph osd dump``. +#. **The OSD Map:** Contains the cluster ``fsid``, the time of the OSD map's + creation, the time of the OSD map's last modification, a list of pools, a + list of replica sizes, a list of PG numbers, and a list of OSDs and their + statuses (for example, ``up``, ``in``). To view an OSD map, run ``ceph + osd dump``. -#. **The PG Map:** Contains the PG version, its time stamp, the last OSD - map epoch, the full ratios, and details on each placement group such as - the PG ID, the `Up Set`, the `Acting Set`, the state of the PG (e.g., - ``active + clean``), and data usage statistics for each pool. +#. **The PG Map:** Contains the PG version, its time stamp, the last OSD map + epoch, the full ratios, and the details of each placement group. This + includes the PG ID, the `Up Set`, the `Acting Set`, the state of the PG (for + example, ``active + clean``), and data usage statistics for each pool. #. **The CRUSH Map:** Contains a list of storage devices, the failure domain - hierarchy (e.g., device, host, rack, row, room, etc.), and rules for - traversing the hierarchy when storing data. To view a CRUSH map, execute - ``ceph osd getcrushmap -o {filename}``; then, decompile it by executing - ``crushtool -d {comp-crushmap-filename} -o {decomp-crushmap-filename}``. - You can view the decompiled map in a text editor or with ``cat``. + hierarchy (for example, ``device``, ``host``, ``rack``, ``row``, ``room``), + and rules for traversing the hierarchy when storing data. To view a CRUSH + map, run ``ceph osd getcrushmap -o {filename}`` and then decompile it by + running ``crushtool -d {comp-crushmap-filename} -o + {decomp-crushmap-filename}``. Use a text editor or ``cat`` to view the + decompiled map. #. **The MDS Map:** Contains the current MDS map epoch, when the map was created, and the last time it changed. It also contains the pool for storing metadata, a list of metadata servers, and which metadata servers are ``up`` and ``in``. To view an MDS map, execute ``ceph fs dump``. -Each map maintains an iterative history of its operating state changes. Ceph -Monitors maintain a master copy of the cluster map including the cluster -members, state, changes, and the overall health of the Ceph Storage Cluster. +Each map maintains a history of changes to its operating state. Ceph Monitors +maintain a master copy of the cluster map. This master copy includes the +cluster members, the state of the cluster, changes to the cluster, and +information recording the overall health of the Ceph Storage Cluster. .. index:: high availability; monitor architecture -- 2.39.5