Merge pull request #209545 from MikeRayMSFT/20220829-resize-pvc

Resize PVC for Arc-enabled data services.

Author: v-regandowner

articles/azure-arc/data/resize-persistent-volume-claim.md

@@ -0,0 +1,112 @@
+---
+title: Resize persistent volume claim (PVC) for Azure Arc-enabled data services volume
+description: Explains how to resize a persistent volume claim for a volume used for Azure Arc-enabled data services.
+services: azure-arc
+ms.service: azure-arc
+ms.subservice: azure-arc-data-sqlmi
+author: dnethi
+ms.author: dinethi
+ms.reviewer: mikeray
+ms.date: 08/29/2022
+ms.topic: how-to
+---
+
+# Resize persistent volume to increase size
+
+This article explains how to resize an existing persistent volume to increase its size by editing the `PersistentVolumeClaim` (PVC) object. 
+
+> [!NOTE]
+> Resizing PVCs using this method only works your `StorageClass` supports `AllowVolumeExpansion=True`.
+
+When you deploy an Azure Arc enabled SQL managed instance, you can configure the size of the persistent volume (PV) for `data`, `logs`, `datalogs`, and `backups`. The deployment creates these volumes based on the values set by parameters `--volume-size-data`, `--volume-size-logs`, `--volume-size-datalogs`, and `--volume-size-backups`. When these volumes become full, you will need to resize the `PersistentVolumes`. Azure Arc enabled SQL Managed Instance is deployed as part of a `StatefulSet` for both General Purpose or Business Critical service tiers. Kubernetes supports automatic resizing for persistent volumes but not for volumes attached to `StatefulSet`. 
+
+Following are the steps to resize persistent volumes attached to `StatefulSet`: 
+
+1. Scale the `StatefulSet` replicas to 0
+2. Patch the PVC to the new size
+3. Scale the `StatefulSet` replicas back to the original size
+
+During the patching of `PersistentVolumeClaim`, the status of the persistent volume claim will likely change from: `Attached` to `Resizing` to `FileSystemResizePending` to `Attached`. The exact states will depend on the storage provisioner. 
+
+> [!NOTE]
+> Ensure the managed instance is in a healthy state before you proceed. Run `kubectl get sqlmi -n <namespace>` and check the status of the managed instance.
+
+## 1. Scale the `StatefulSet` replicas to 0
+
+There is one `StatefulSet` deployed for each Arc SQL MI. The number of replicas in the `StatefulSet` is equal to the number of replicas in the Arc SQL MI. For General Purpose service tier, this is 1. For Business Critical service tier it could be 1, 2 or 3 depending on how many replicas were specified. Run the below command to get the number of `StatefulSet` replicas if you have a Business Critical instance. 
+
+```console
+kubectl get sts --namespace  <namespace>
+```
+
+For example, if the namespace is `arc`, run:
+
+```console
+kubectl get sts --namespace arc
+```
+
+Notice the number of stateful sets under the `READY` column for the SQL managed instance(s).
+
+Run the below command to scale the `StatefulSet` replicas to 0:
+
+```console
+kubectl scale statefulsets <statefulset> --namespace <namespace> --replicas= <number>
+```
+
+For example:
+
+```console
+kubectl scale statefulsets sqlmi1 --namespace arc --replicas=0
+```
+
+## 2. Patch the PVC to the new size
+
+Run the below command to get the name of the `PersistentVolumeClaim` which needs to be resized:
+
+```console
+kubectl get pvc --namespace <namespace>
+```
+
+For example:
+
+```console
+kubectl get pvc --namespace arc
+```
+
+
+Once the stateful `StatefulSet` replicas have completed scaling down to 0, patch the  `StatefulSet`. Run the following command:
+
+```console
+$newsize='{\"spec\":{\"resources\":{\"requests\":{\"storage\":\"<newsize>Gi\"}}}}'
+kubectl patch pvc <name of PVC> --namespace <namespace> --type merge --patch $newsize
+```
+
+For example: the following command will resize the data PVC to 50Gi. 
+
+```console
+$newsize='{\"spec\":{\"resources\":{\"requests\":{\"storage\":\"50Gi\"}}}}'
+kubectl patch pvc data-a6gt3be7mrtq60eao0gmgxgd-sqlmi1-0 --namespace arcns --type merge --patch $newsize
+```
+
+## 3. Scale the `StatefulSet` replicas to original size
+
+Once the resize completes, scale the `StatefulSet` replicas back to its original size by running the below command:
+
+```console
+kubectl scale statefulsets <statefulset> --namespace <namespace> --replicas= <number>
+```
+
+For example: The below command sets the `StatefulSet` replicas to 3.
+
+```
+kubectl scale statefulsets sqlmi1 --namespace arc --replicas=3
+```
+Ensure the Arc enabled SQL managed instance is back to ready status by running:
+
+```console
+kubectl get sqlmi -A
+```
+
+## See also
+
+[Sizing Guidance](sizing-guidance.md)

articles/azure-arc/data/toc.yml

@@ -150,6 +150,8 @@ items:
               href: reserved-capacity-overview.md
             - name: Rotate certificates
               href: rotate-user-tls-certificate.md
+            - name: Resize persistent volume (PVC)
+              href: resize-persistent-volume-claim.md
             - name: Delete
               href: delete-managed-instance.md
         - name: Upgrade