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https://github.com/cgwalters/coreos-cloud-instance-store-provisioner

Provision instance storage on CoreOS
https://github.com/cgwalters/coreos-cloud-instance-store-provisioner

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Provision instance storage on CoreOS

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# Prototype code to automatically set up instance storage for CoreOS

This is WIP for https://hackmd.io/dTUvY7BIQIu_vFK5bMzYvg

## Quickstart w/OpenShift 4 (for workers)

Supported platforms:

- AWS (e.g. `m5d` instances)
- Azure
- qemu (for quick local testing)

### Create a MachineConfig to set this up:

`oc create -f 50-worker-coreos-cloud-instance-store-provisioner.yaml`

Wait for the worker MCP to roll out to the latest (`oc get machineconfigpool/worker`).
Note: Existing machines will be reconfigured but do not actually change state in practice.

### AWS: Edit the machineset to use a m5d type that has instance storage

On AWS, if you haven't created the cluster with this by default, you need to:
`oc -n openshift-machine-api edit machineset/$x` and change the instance type use e.g. `m5d.xlarge` (150GiB instance store).

Then scale up the machineset:
`oc -n openshift-machine-api scale machineset/$x`
When the new node joins the cluster, use e.g. `oc debug node/$node` and inspect `findmnt /var/lib/containers` - it should be a bind mount.

### Azure: Default machine types have instance storage already

In current IPI Azure installs the default `Standard_D8s_v3` machine type has 32GB of instance storage by default.

## Configuring the control plane

You can also configure the control plane to use this; there are
two variants of that - one for just the control plane's `/var/lib/containers`,
and one including that and `/var/lib/etcd`. Doing both is by far
the most interesting; if you don't have a schedulable control
plane then just doing `/var/lib/containers` won't change too much.

You must configure the control plane "day 0" by providing
[additional manifests to the installer](https://github.com/openshift/installer/blob/master/docs/user/customization.md#install-time-customization-for-machine-configuration).

There is a `50-master-coreos-cloud-instance-store-provisioner.yaml`
you can use that is set up to do both directories. Get ready
for much improved etcd performance!

(Tip: You may like using [xokdinst](https://github.com/cgwalters/xokdinst)
which makes it much [more ergonomic to provide additional manifests](https://github.com/cgwalters/xokdinst#nicer-flow-for-injecting-manifests),
among other things, but it's just an `openshift-install` wrapper.)

## Benchmarks

None yet. You could be the first on your block to do it!

## Support for losing the instance store

I tested with this simple script:

```
#!/bin/bash
systemctl stop kubelet
systemctl stop cri-o
rm -rf /var/mnt/instance-storage/* -rf
reboot
```

The worker node rebooted and came back just fine.