# Local Static Storage Provisioner

The [local static storage provisioner](https://github.com/kubernetes-sigs/sig-storage-local-static-provisioner)
is NOT a dynamic storage provisioner as you would
expect from a cloud provider. Instead, it simply creates PersistentVolumes for
all mounts under the `host_dir` of the specified storage class.
These storage classes are specified in the `local_volume_provisioner_storage_classes` nested dictionary.

Example:

```yaml
local_volume_provisioner_storage_classes:
  local-storage:
    host_dir: /mnt/disks
    mount_dir: /mnt/disks
  fast-disks:
    host_dir: /mnt/fast-disks
    mount_dir: /mnt/fast-disks
    block_cleaner_command:
      - "/scripts/shred.sh"
      - "2"
    volume_mode: Filesystem
    fs_type: ext4
```

For each key in `local_volume_provisioner_storage_classes` a "storage class" with
the same name is created in the entry `storageClassMap` of the ConfigMap `local-volume-provisioner`.
The subkeys of each storage class in `local_volume_provisioner_storage_classes`
are converted to camelCase and added as attributes to the storage class in the
ConfigMap.

The result of the above example is:

```yaml
data:
  storageClassMap: |
    local-storage:
      hostDir: /mnt/disks
      mountDir: /mnt/disks
    fast-disks:
      hostDir: /mnt/fast-disks
      mountDir:  /mnt/fast-disks
      blockCleanerCommand:
        - "/scripts/shred.sh"
        - "2"
      volumeMode: Filesystem
      fsType: ext4
```

Additionally, a StorageClass object (`storageclasses.storage.k8s.io`) is also
created for each storage class:

```bash
$ kubectl get storageclasses.storage.k8s.io
NAME            PROVISIONER                    RECLAIMPOLICY
fast-disks      kubernetes.io/no-provisioner   Delete
local-storage   kubernetes.io/no-provisioner   Delete
```

The default StorageClass is `local-storage` on `/mnt/disks`;
the rest of this documentation will use that path as an example.

## Examples to create local storage volumes

1. Using tmpfs

   ```bash
   for vol in vol1 vol2 vol3; do
     mkdir /mnt/disks/$vol
     mount -t tmpfs -o size=5G $vol /mnt/disks/$vol
   done
   ```

   The tmpfs method is not recommended for production because the mounts are not
   persistent and data will be deleted on reboot.

1. Mount physical disks

   ```bash
   mkdir /mnt/disks/ssd1
   mount /dev/vdb1 /mnt/disks/ssd1
   ```

   Physical disks are recommended for production environments because it offers
   complete isolation in terms of I/O and capacity.

1. Mount unpartitioned physical devices

   ```bash
   for disk in /dev/sdc /dev/sdd /dev/sde; do
     ln -s $disk /mnt/disks
   done
   ```

   This saves time of precreating filesystems. Note that your storageclass must have
   `volume_mode` set to `"Filesystem"` and `fs_type` defined. If either is not set, the
   disk will be added as a raw block device.

1. PersistentVolumes with `volumeMode="Block"`

   Just like above, you can create PersistentVolumes with volumeMode `Block`
   by creating a symbolic link under discovery directory to the block device on
   the node, if you set `volume_mode` to `"Block"`. This will create a volume
   presented into a Pod as a block device, without any filesystem on it.

1. File-backed sparsefile method

   ```bash
   truncate /mnt/disks/disk5 --size 2G
   mkfs.ext4 /mnt/disks/disk5
   mkdir /mnt/disks/vol5
   mount /mnt/disks/disk5 /mnt/disks/vol5
   ```

   If you have a development environment and only one disk, this is the best way
   to limit the quota of persistent volumes.

1. Simple directories

   In a development environment, using `mount --bind` works also, but there is no capacity
   management.

## Usage notes

Make sure to make any mounts persist via `/etc/fstab` or with systemd mounts (for
Flatcar Container Linux or Fedora CoreOS). Pods with persistent volume claims will not be
able to start if the mounts become unavailable.

## Further reading

Refer to the upstream docs here: <https://github.com/kubernetes-sigs/sig-storage-local-static-provisioner>