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docs: improve CSI deployment recommendations (#10798)

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* add some more context to the recommendations
* add recommendations around per-AZ `plugin_id`
This commit is contained in:
Tim Gross
2021-06-22 10:23:09 -04:00
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parent b430bafe90
commit 3fdbbeefe0
1 changed files with 23 additions and 8 deletions
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website/content/docs/job-specification/csi_plugin.mdx
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@@ -49,15 +49,30 @@ host. With the Docker task driver, you can use the `privileged = true`
configuration, but no other default task drivers currently have this
option.
~> **Note:** During node drains, jobs that claim volumes must be moved before
the `node` or `monolith` plugin for those volumes. You should run `node` or
`monolith` plugins as [`system`][system] jobs and use the `-ignore-system`
flag on `nomad node drain` to ensure that the plugins are running while the
node is being drained.
## Recommendations for Deploying CSI Plugins
~> **Note:** Only one plugin instance of a given plugin ID and type
(controller or node) should be deployed on any given client node. Use a
constraint as shown below.
CSI plugins run as Nomad jobs but after mounting the volume are not in the
data path for the volume. Jobs that mount volumes write and read directly to
the volume via a bind-mount and there is no communication between the job and
the CSI plugin. But when an allocation that mounts a volume stops, Nomad will
need to communicate with the plugin on that allocation's node to unmount the
volume. This has implications on how to deploy CSI plugins:
* During node drains, jobs that claim volumes must be moved before the `node`
or `monolith` plugin for those volumes. You should run `node` or `monolith`
plugins as [`system`][system] jobs and use the `-ignore-system` flag on
`nomad node drain` to ensure that the plugins are running while the node is
being drained.
* Only one plugin instance of a given plugin ID and type (controller or node)
should be deployed on any given client node. Use a constraint as shown
below.
* Some plugins will create volumes only in the same location as the
plugin. For example, the AWS EBS plugin will create and mount volumes only
within the same Availability Zone. You should deploy these plugins with a
unique-per-AZ `plugin_id` to allow Nomad to place allocations in the correct
AZ.
## `csi_plugin` Examples