OpenEBS ZFS CSI Driver

CSI driver for provisioning Local PVs backed by ZFS and more.

Project Status

ZFS-LocalPV was declared GA in Dec 2020. Many users are running ZFS-LocalPV in production, see what our adopters are saying.

Project Tracker

See roadmap, e2e-wiki and e2e-test.

Usage

Prerequisites

Before installing ZFS driver please make sure your Kubernetes Cluster must meet the following prerequisites:

1. all the nodes must have zfs utils installed
2. ZPOOL has been setup for provisioning the volume
3. You have access to install RBAC components into kube-system namespace. The OpenEBS ZFS driver components are installed in kube-system namespace to allow them to be flagged as system critical components.

Supported System

K8S : 1.20+

OS : Ubuntu, CentOS

ZFS : 0.7, 0.8

Check the features supported for each k8s version.

Setup

All the node should have zfsutils-linux installed. We should go to the each node of the cluster and install zfs utils

$ apt-get install zfsutils-linux

Go to each node and create the ZFS Pool, which will be used for provisioning the volumes. You can create the Pool of your choice, it can be striped, mirrored or raidz pool.

If you have the disk(say /dev/sdb) then you can use the below command to create a striped pool:

zpool create zfspv-pool /dev/sdb

You can also create mirror or raidz pool as per your need. Check https://github.com/openzfs/zfs for more information.

If you don't have the disk, then you can create the zpool on the loopback device which is backed by a sparse file. Use this for testing purpose only.

truncate -s 100G /tmp/disk.img
zpool create zfspv-pool `sudo losetup -f /tmp/disk.img --show`

Once the ZFS Pool is created, verify the pool via zpool status command, you should see something like this :

$ sudo zpool status
  pool: zfspv-pool
 state: ONLINE
  scan: none requested
config:

	NAME        STATE     READ WRITE CKSUM
	zfspv-pool  ONLINE       0     0     0
	  sdb       ONLINE       0     0     0

errors: No known data errors

Configure the custom topology keys (if needed). This can be used for many purposes like if we want to create the PV on nodes in a particuler zone or building. We can label the nodes accordingly and use that key in the storageclass for taking the scheduling decesion:

https://github.com/openebs/zfs-localpv/blob/HEAD/docs/faq.md#6-how-to-add-custom-topology-key

Installation

We can install the latest release of OpenEBS ZFS driver by running the following command.

$ kubectl apply -f https://openebs.github.io/charts/zfs-operator.yaml

We can also install it via kustomize using kubectl apply -k deploy/yamls, check the kustomize yaml.

NOTE: If you are running a custom Kubelet location, or a Kubernetes distribution that uses a custom Kubelet location, the kubelet directory must be changed at all relevant places in the YAML powering the operator (both the openebs-zfs-controller and openebs-zfs-node).

• For microk8s, we need to change the kubelet directory to /var/snap/microk8s/common/var/lib/kubelet/, we need to replace /var/lib/kubelet/ with /var/snap/microk8s/common/var/lib/kubelet/ at all the places in the operator yaml and then we can apply it on microk8s.

• For k0s, the default directory (/var/lib/kubelet) should be changed to /var/lib/k0s/kubelet.

• For RancherOS, the default directory (/var/lib/kubelet) should be changed to /opt/rke/var/lib/kubelet.

Verify that the ZFS driver Components are installed and running using below command :

$ kubectl get pods -n kube-system -l role=openebs-zfs

Depending on number of nodes, you will see one zfs-controller pod and zfs-node daemonset running on the nodes.

NAME                       READY   STATUS    RESTARTS   AGE
openebs-zfs-controller-0   5/5     Running   0          5h28m
openebs-zfs-node-4d94n     2/2     Running   0          5h28m
openebs-zfs-node-gssh8     2/2     Running   0          5h28m
openebs-zfs-node-twmx8     2/2     Running   0          5h28m

Once ZFS driver is installed we can provision a volume.

Deployment

1. Create a Storage class

$ cat sc.yaml

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-zfspv
parameters:
  recordsize: "128k"
  compression: "off"
  dedup: "off"
  fstype: "zfs"
  poolname: "zfspv-pool"
provisioner: zfs.csi.openebs.io

The storage class contains the volume parameters like recordsize(should be power of 2), compression, dedup and fstype. You can select what are all parameters you want. In case, zfs properties paramenters are not provided, the volume will inherit the properties from the ZFS Pool. The poolname is the must argument. It should be noted that poolname can either be the root dataset or a child dataset e.g.

poolname: "zfspv-pool"
poolname: "zfspv-pool/child"

Also the dataset provided under poolname must exist on all the nodes with the name given in the storage class. Check the doc on storageclasses to know all the supported parameters for ZFS-LocalPV

ext2/3/4 or xfs or btrfs as FsType

If we provide fstype as ext2/3/4 or xfs or btrfs, the driver will create a ZVOL, which is a blockdevice carved out of ZFS Pool. This blockdevice will again formatted as corresponding filesystem(ext2/3/4 or xfs). In this way applications will get desired filesystem. Here, in this case there will be a filesystem layer on top of ZFS filesystem, and applications may not get the optimal performance. The sample storage class for ext4 fstype is provided below :-

$ cat sc.yaml

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-zfspv
parameters:
  volblocksize: "4k"
  compression: "off"
  dedup: "off"
  fstype: "ext4"
  poolname: "zfspv-pool"
provisioner: zfs.csi.openebs.io

Here please note that we are providing volblocksize instead of recordsize since we will create a ZVOL, for which we can choose the blocksize with which we want to create the block device. Here, please note that for ZFS, volblocksize should be power of 2.

zfs as FsType

In case if we provide "zfs" as the fstype, the zfs driver will create ZFS DATASET in the ZFS Pool, which is the zfs filesystem. Here, there will not be any extra layer between application and storage, and applications can get the optimal performance. The sample storage class for zfs fstype is provided below :-

$ cat sc.yaml

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-zfspv
parameters:
  recordsize: "128k"
  compression: "off"
  dedup: "off"
  fstype: "zfs"
  poolname: "zfspv-pool"
provisioner: zfs.csi.openebs.io

Here please note that we are providing recordsize which will be used to create the ZFS datasets, which specifies the maximum block size for files in the zfs file system. The recordsize has to be power of 2 for ZFS datasets.

ZPOOL Availability

If ZFS pool is available on certain nodes only, then make use of topology to tell the list of nodes where we have the ZFS pool available. As shown in the below storage class, we can use allowedTopologies to describe ZFS pool availability on nodes.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-zfspv
allowVolumeExpansion: true
parameters:
  recordsize: "128k"
  compression: "off"
  dedup: "off"
  fstype: "zfs"
  poolname: "zfspv-pool"
provisioner: zfs.csi.openebs.io
allowedTopologies:
- matchLabelExpressions:
  - key: kubernetes.io/hostname
    values:
      - zfspv-node1
      - zfspv-node2

The above storage class tells that ZFS pool "zfspv-pool" is available on nodes zfspv-node1 and zfspv-node2 only. The ZFS driver will create volumes on those nodes only.

Please note that the provisioner name for ZFS driver is "zfs.csi.openebs.io", we have to use this while creating the storage class so that the volume provisioning/deprovisioning request can come to ZFS driver.

Scheduler

The ZFS driver has its own scheduler which will try to distribute the PV across the nodes so that one node should not be loaded with all the volumes. Currently the driver supports two scheduling algorithms: VolumeWeighted and CapacityWeighted, in which it will try to find a ZFS pool which has less number of volumes provisioned in it or less capacity of volume provisioned out of a pool respectively, from all the nodes where the ZFS pools are available. To know about how to select scheduler via storage-class See this. Once it is able to find the node, it will create a PV for that node and also create a ZFSVolume custom resource for the volume with the NODE information. The watcher for this ZFSVolume CR will get all the information for this object and creates a ZFS dataset(zvol) with the given ZFS property on the mentioned node.

The scheduling algorithm currently only accounts for either the number of ZFS volumes or total capacity occupied from a zpool and does not account for other factors like available cpu or memory while making scheduling decisions. So if you want to use node selector/affinity rules on the application pod, or have cpu/memory constraints, kubernetes scheduler should be used. To make use of kubernetes scheduler, you can set the volumeBindingMode as WaitForFirstConsumer in the storage class. This will cause a delayed binding, i.e kubernetes scheduler will schedule the application pod first and then it will ask the ZFS driver to create the PV. The driver will then create the PV on the node where the pod is scheduled.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-zfspv
allowVolumeExpansion: true
parameters:
  recordsize: "128k"
  compression: "off"
  dedup: "off"
  fstype: "zfs"
  poolname: "zfspv-pool"
provisioner: zfs.csi.openebs.io
volumeBindingMode: WaitForFirstConsumer

Please note that once a PV is created for a node, application using that PV will always get scheduled to that particular node only, as PV will be sticky to that node. The scheduling algorithm by ZFS driver or kubernetes will come into picture only during the deployment time. Once the PV is created, the application can not move anywhere as the data is there on the node where the PV is.

2. Create the PVC

$ cat pvc.yaml

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: csi-zfspv
spec:
  storageClassName: openebs-zfspv
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 4Gi

Create a PVC using the storage class created for the ZFS driver. Here, the allocated volume size will be rounded off to the nearest Mi or Gi notation, check the faq section for more details.

If we are using the immediate binding in the storageclass then we can check the kubernetes resource for the corresponding zfs volume, other wise in late binding case, we can check the same after pod has been scheduled.

$ kubectl get zv -n openebs
NAME                                       ZPOOL        NODE           SIZE         STATUS   FILESYSTEM   AGE
pvc-34133838-0d0d-11ea-96e3-42010a800114   zfspv-pool   zfspv-node1    4294967296   Ready    zfs          4s

$ kubectl describe zv pvc-34133838-0d0d-11ea-96e3-42010a800114 -n openebs
Name:         pvc-34133838-0d0d-11ea-96e3-42010a800114
Namespace:    openebs
Labels:       kubernetes.io/nodename=zfspv-node1
Annotations:  <none>
API Version:  openebs.io/v1alpha1
Kind:         ZFSVolume
Metadata:
  Creation Timestamp:  2019-11-22T09:49:29Z
  Finalizers:
    zfs.openebs.io/finalizer
  Generation:        1
  Resource Version:  2881
  Self Link:         /apis/openebs.io/v1alpha1/namespaces/openebs/zfsvolumes/pvc-34133838-0d0d-11ea-96e3-42010a800114
  UID:               60bc4df2-0d0d-11ea-96e3-42010a800114
Spec:
  Capacity:       4294967296
  Compression:    off
  Dedup:          off
  Fs Type:        zfs
  Owner Node ID:  zfspv-node1
  Pool Name:      zfspv-pool
  Recordsize:     4k
  Volume Type:    DATASET
Status:
  State: Ready
Events:           <none>

The ZFS driver will create a ZFS dataset(or zvol as per fstype in the storageclass) on the node zfspv-node1 for the mentioned ZFS pool and the dataset name will same as PV name. Go to the node zfspv-node1 and check the volume :-

$ zfs list
NAME                                                  USED  AVAIL  REFER  MOUNTPOINT
zfspv-pool                                            444K   362G    96K  /zfspv-pool
zfspv-pool/pvc-34133838-0d0d-11ea-96e3-42010a800114    96K  4.00G    96K  legacy

3. Deploy the application

Create the deployment yaml using the pvc backed by ZFS-LocalPV storage.

$ cat fio.yaml

apiVersion: v1
kind: Pod
metadata:
  name: fio
spec:
  restartPolicy: Never
  containers:
  - name: perfrunner
    image: openebs/tests-fio
    command: ["/bin/bash"]
    args: ["-c", "while true ;do sleep 50; done"]
    volumeMounts:
       - mountPath: /datadir
         name: fio-vol
    tty: true
  volumes:
  - name: fio-vol
    persistentVolumeClaim:
      claimName: csi-zfspv

After the deployment of the application, we can go to the node and see that the zfs volume is being used by the application for reading/writting the data and space is consumed from the ZFS pool.

4. ZFS Property Change

ZFS Volume Property can be changed like compression on/off can be done by just simply editing the kubernetes resource for the corresponding zfs volume by using below command :

kubectl edit zv pvc-34133838-0d0d-11ea-96e3-42010a800114 -n openebs

You can edit the relevant property like make compression on or make dedup on and save it. This property will be applied to the corresponding volume and can be verified using below command on the node:

zfs get all zfspv-pool/pvc-34133838-0d0d-11ea-96e3-42010a800114

5. Deprovisioning

for deprovisioning the volume we can delete the application which is using the volume and then we can go ahead and delete the pv, as part of deletion of pv this volume will also be deleted from the ZFS pool and data will be freed.

$ kubectl delete -f fio.yaml
pod "fio" deleted
$ kubectl delete -f pvc.yaml
persistentvolumeclaim "csi-zfspv" deleted

CAUTION:

Follow below practice while running kernel ZFS along with cStor on the same set of nodes

• Disable zfs-import-scan.service service that will avoid importing all pools by scanning all the available devices in the system, disabling scan service will avoid importing pools that are not created by kernel. Disabling scan service will not cause harm since zfs-import-cache.service is enabled and it is the best way to import pools by looking at cache file during boot time.

sudo systemctl stop zfs-import-scan.service
sudo systemctl disable zfs-import-scan.service

• Always maintain upto date /etc/zfs/zpool.cache while performing operations any day2 operations on zfs pools(zpool set cachefile=/etc/zfs/zpool.cache ).

Note: Following above two step kernel ZFS will not import the pools created by cStor

Features

• Access Modes
  • ReadWriteOnce
  • ReadOnlyMany
  • ReadWriteMany
• Volume modes
  • Filesystem mode
  • Block mode
• Supports fsTypes: ext4, btrfs, xfs, zfs
• Volume metrics
• Snapshot
• Clone
• Volume Resize
• Raw Block Volume
• Backup/Restore
• Ephemeral inline volume

License