Windows Storage [page]deterministic
This page provides an storage overview specific to the Windows operating system.
## Persistent storage {#storage}
Windows has a layered filesystem driver to mount container layers and create a copy filesystem based on NTFS. All file paths in the container are resolved only within the context of that container.
* With Docker, volume mounts can only target a directory in the container, and not an individual file. This limitation does not apply to containerd. * Volume mounts cannot project files or directories back to the host filesystem. * Read-only filesystems are not supported because write access is always required for the Windows registry and SAM database. However, read-only volumes are supported. * Volume user-masks and permissions are not available. Because the SAM is not shared between the host & container, there's no mapping between them. All permissions are resolved within the context of the container.
As a result, the following storage functionality is not supported on Windows nodes:
* Volume subpath mounts: only the entire volume can be mounted in a Windows container * Subpath volume mounting for Secrets * Host mount projection * Read-only root filesystem (mapped volumes still support `readOnly`) * Block device mapping * Memory as the storage medium (for example, `emptyDir.medium` set to `Memory`) * File system features like uid/gid; per-user Linux filesystem permissions * Setting [secret permissions with DefaultMode](/docs/tasks/inject-data-application/distribute-credentials-secure/#set-posix-permissions-for-secret-keys) (due to UID/GID dependency) * NFS based storage/volume support * Expanding the mounted volume (resizefs)
Kubernetes [volumes](#gloss:volume) enable complex applications, with data persistence and Pod volume sharing requirements, to be deployed on Kubernetes. Management of persistent volumes associated with a specific storage back-end or protocol includes actions such as provisioning/de-provisioning/resizing of volumes, attaching/detaching a volume to/from a Kubernetes node and mounting/dismounting a volume to/from individual containers in a pod that needs to persist data.
Volume management components are shipped as Kubernetes volume [plugin](/docs/concepts/storage/volumes/#volume-types). The following broad classes of Kubernetes volume plugins are supported on Windows:
* [`FlexVolume plugins`](/docs/concepts/storage/volumes/#flexvolume) * Please note that FlexVolumes have been deprecated as of 1.23 * [`CSI Plugins`](/docs/concepts/storage/volumes/#csi)
##### In-tree volume plugins
The following in-tree plugins support persistent storage on Windows nodes:
* [`azureFile`](/docs/concepts/storage/volumes/#azurefile) * [`vsphereVolume`](/docs/concepts/storage/volumes/#vspherevolume)