From 6f080590b6da6a546fcc55a688f22096ad7bb58a Mon Sep 17 00:00:00 2001 From: Frank Kloeker Date: Tue, 21 May 2019 14:35:14 +0200 Subject: [PATCH] Fix documentation for usage of Nova Cells (v2) Change-Id: I979a8542a013b1165591c7601de774b9da276dce Closes-Bug: #1804253 --- doc/source/ops-capacity-planning-scaling.rst | 30 +++++++++----------- 1 file changed, 14 insertions(+), 16 deletions(-) diff --git a/doc/source/ops-capacity-planning-scaling.rst b/doc/source/ops-capacity-planning-scaling.rst index 07c91f0f..915dc402 100644 --- a/doc/source/ops-capacity-planning-scaling.rst +++ b/doc/source/ops-capacity-planning-scaling.rst @@ -197,8 +197,8 @@ segregation method currently provided by OpenStack Compute. - Availability zones - Host aggregates * - **Use** - - A single :term:`API endpoint` for compute, or you require a second - level of scheduling. + - Shard and scale compute deployment while maintaining a single + :term:`API endpoint`. - Discrete regions with separate API endpoints and no coordination between regions. - Logical separation within your nova deployment for physical isolation @@ -212,8 +212,8 @@ segregation method currently provided by OpenStack Compute. - A single-site cloud with equipment fed by separate power supplies. - Scheduling to hosts with trusted hardware support. * - **Overhead** - - Considered experimental. A new service, nova-cells. Each cell has a full - nova installation except nova-api. + - Each Cell contains instances of services with overlapping + functionality. - A different API endpoint for every region. Each region has a full nova installation. - Configuration changes to ``nova.conf``. @@ -227,22 +227,20 @@ segregation method currently provided by OpenStack Compute. Cells and regions ----------------- -OpenStack Compute cells are designed to allow running the cloud in a +`OpenStack Compute Cells `_ +are designed to allow running the cloud in a distributed fashion without having to use more complicated technologies, or be invasive to existing nova installations. Hosts in a cloud are -partitioned into groups called *cells*. Cells are configured in a tree. -The top-level cell ("API cell") has a host that runs the ``nova-api`` -service, but no ``nova-compute`` services. Each child cell runs all of -the other typical ``nova-*`` services found in a regular installation, -except for the ``nova-api`` service. Each cell has its own message queue -and database service and also runs ``nova-cells``, which manages the -communication between the API cell and child cells. +partitioned into groups called *Cells*. Cells are configured in a tree. +The top-level Cell ("API cell") has a host that runs the ``nova-api`` +service, but no ``nova-compute`` services. The ``nova-compute`` runs +in a child Cell. +Each Cell has its own message queue and database service. This allows for a single API server being used to control access to -multiple cloud installations. Introducing a second level of scheduling -(the cell selection), in addition to the regular ``nova-scheduler`` -selection of hosts, provides greater flexibility to control where -virtual machines are run. +multiple compute installations with the usage of multiple Cells. +See `Nova Cells V2 Layout `_ +for further documentation. Unlike having a single API endpoint, regions have a separate API endpoint per installation, allowing for a more discrete separation.