81 lines
3.1 KiB
Markdown
81 lines
3.1 KiB
Markdown
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# Volume Expansion
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## Overview
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- Longhorn supports both ONLINE and OFFLINE volume expansion.
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- Longhorn will expand frontend (e.g. block device) then expand filesystem.
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## Prerequisite:
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Longhorn version v0.8.0 or higher.
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## Expand a Longhorn volume
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There are two ways to expand a Longhorn volume:
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#### Via PVC
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- This method is applied only if:
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1. Kubernetes version v1.16 or higher.
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2. The PVC is dynamically provisioned by the Kubernetes with Longhorn StorageClass.
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3. The field `allowVolumeExpansion` should be `true` in the related StorageClass.
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- This method is recommended if it's applicable. Since the PVC and PV will be updated automatically and everything keeps consistent after expansion.
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- Usage: Find the corresponding PVC for Longhorn volume then modify requested `storage` of the PVC spec. e.g.,
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```
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apiVersion: v1
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kind: PersistentVolumeClaim
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metadata:
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annotations:
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kubectl.kubernetes.io/last-applied-configuration: |
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{"apiVersion":"v1","kind":"PersistentVolumeClaim","metadata":{"annotations":{},"name":"longhorn-simple-pvc","namespace":"default"},"spec":{"accessModes":["ReadWriteOnce"],"resources":{"requests":{"storage":"1Gi"}},"storageClassName":"longhorn"}}
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pv.kubernetes.io/bind-completed: "yes"
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pv.kubernetes.io/bound-by-controller: "yes"
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volume.beta.kubernetes.io/storage-provisioner: driver.longhorn.io
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creationTimestamp: "2019-12-21T01:36:16Z"
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finalizers:
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- kubernetes.io/pvc-protection
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name: longhorn-simple-pvc
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namespace: default
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resourceVersion: "162431"
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selfLink: /api/v1/namespaces/default/persistentvolumeclaims/longhorn-simple-pvc
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uid: 0467ae73-22a5-4eba-803e-464cc0b9d975
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spec:
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accessModes:
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- ReadWriteOnce
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resources:
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requests:
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storage: 1Gi
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storageClassName: longhorn
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volumeMode: Filesystem
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volumeName: pvc-0467ae73-22a5-4eba-803e-464cc0b9d975
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status:
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accessModes:
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- ReadWriteOnce
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capacity:
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storage: 1Gi
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phase: Bound
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```
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Modify `spec.resources.requests.storage` of this PVC.
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#### Via Longhorn UI
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- If your Kubernetes version is v1.14 or v1.15, this method is the only choice for Longhorn volume expansion.
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- Notice that The volume size will be updated after the expansion but the capacity of corresponding PVC and PV won't change. Users need to take care of them.
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- Usage: On the volume page of Longhorn UI, click `Expand` for the volume.
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## Frontend expansion
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- Longhorn will expand a Longhorn volume's frontend even if the volume is in the maintenance mode.
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- For the OFFLINE expansion, Longhorn will automatically attach the `detached` volume to a random node then do expansion.
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For the ONLINE expansion, users can read/write the volume while expansion.
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- Rebuilding/adding replicas is not allowed during the expansion and vice versa.
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## Filesystem expansion
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Longhorn will try to expand the file system only if:
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1. The expanded size should be greater than the current size.
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2. There is a Linux filesystem in the Longhorn volume.
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3. The filesystem used in the Longhorn volume is one of the followings:
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3.1 ext4
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3.2 XFS
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4. The Longhorn volume is not in maintanence mode
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5. The Longhorn volume is using block device frontend.
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