AV

Aarthi-Vijayaraghavan · Aarthi-Vijayaraghavan · commit 4d8b8f82b0b3 · 2021-10-25T22:57:08.000+05:30
diff --git a/articles/virtual-machines/ephemeral-os-disks.md b/articles/virtual-machines/ephemeral-os-disks.md
@@ -19,21 +19,19 @@ Ephemeral OS disks are created on the local virtual machine (VM) storage and not
  
 The key features of ephemeral disks are: 
 - Ideal for stateless applications.
-- They can be used with both Marketplace and custom images.
+- Supported by  Marketplace, custom images, and by [Shared Image Gallery](./shared-image-galleries.md).
 - Ability to fast reset or reimage VMs and scale set instances to the original boot state.  
 - Lower latency, similar to a temporary disk. 
-- Ephemeral OS disks are free, you incur no storage cost for OS disk.
-- Available in all Azure regions. 
-- Ephemeral OS Disk is supported by [Shared Image Gallery](./shared-image-galleries.md). 
- 
+- Ephemeral OS disks are free, you incur no storage cost for OS disks.
+- Available in all Azure regions.  
 
  
 Key differences between persistent and ephemeral OS disks:
 
 |                             | Persistent OS Disk                          | Ephemeral OS Disk                              |
 |-----------------------------|---------------------------------------------|------------------------------------------------|
 | **Size limit for OS disk**      | 2 TiB                                                                                        | Cache size for the VM size or 2 TiB, whichever is smaller. For the **cache size in GiB**, see [DS](sizes-general.md), [ES](sizes-memory.md), [M](sizes-memory.md), [FS](sizes-compute.md), and [GS](sizes-previous-gen.md#gs-series)              |
-| **VM sizes supported**          | All                                                                                          | VM sizes that support Premium storage such as DSv1, DSv2, DSv3, Esv3, Fs, FsV2, GS, M                                               |
+| **VM sizes supported**          | All                                                                                          | VM sizes that support Premium storage such as DSv1, DSv2, DSv3, Esv3, Fs, FsV2, GS, M, Mdsv2,Bs, Dav4, Eav4                                               |
 | **Disk type support**           | Managed and unmanaged OS disk                                                                | Managed OS disk only                                                               |
 | **Region support**              | All regions                                                                                  | All regions                              |
 | **Data persistence**            | OS disk data written to OS disk are stored in Azure Storage                                  | Data written to OS disk is stored on local VM storage and isn't persisted to Azure Storage. |
@@ -43,68 +41,38 @@ Key differences between persistent and ephemeral OS disks:
 | **Resizing to a new VM size**   | OS disk data is preserved                                                                    | Data on the OS disk is deleted, OS is reprovisioned       
 | **Page file placement**   | For Windows, page file is stored on the resource disk                                              | For Windows, page file is stored on the OS disk (for both OS cache placement and Temp disk placement).   |
 
-
 ## Size requirements
 
 You can choose to deploy Ephemeral OS Disk on VM cache or VM temp disk.
-The image OS disk’s size should be equal to or greater than the temp/cache size of the disk chosen.
+The image OS disk’s size should be less than or equal to the temp/cache size of the VM size chosen.
 
 For example, if you want to opt for **OS cache placement**: Standard Windows Server images from the marketplace are about 127 GiB, which means that you need a VM size that has a cache equal to or larger than 127 GiB. The Standard_DS3_v2 has a cache size of 127 GiB, which is large enough. In this case, the Standard_DS3_v2 is the smallest size in the DSv2 series that you can use with this image. 
 
-If you want to opt for **Temp disk placement**: Standard Ubuntu server image from marketplace comes with 30-GiB OS disk space. To enable Ephemeral OS disk, the disk size must be equal to or larger than 30 GiB. Standard_B4ms has a temp size of 32 GiB, which can fit the 30 GiB OS disk. But Standard_B2ms has a temp size of 16 GiB, which wouldn't be able to fit 30 GiB of OS disk.
+If you want to opt for **Temp disk placement**: Standard Ubuntu server image from marketplace is about 30 GiB. To enable Ephemeral OS disk on temp, the temp disk size must be equal to or larger than 30 GiB. Standard_B4ms has a temp size of 32 GiB, which can fit the 30 GiB OS disk. Upon creation of the VM, the temp disk space would be 2 GiB. 
+> [!Important] If opting for temp disk placement the Final Temp disk size = (Initial temp disk size - OS image size).
 
 Basic Linux and Windows Server images in the Marketplace that are denoted by `[smallsize]` tend to be around 30 GiB and can use most of the available VM sizes.
 Ephemeral disks also require that the VM size supports **Premium storage**. The sizes usually (but not always) have an `s` in the name, like DSv2 and EsV3. For more information, see [Azure VM sizes](sizes.md) for details around which sizes support Premium storage.
 
-
 ## Ephemeral OS Disks can now be stored on temp/Resource disks
 Ephemeral OS disk can now be stored either in VM cache disk or VM temp/resource disk. 
-This feature enables Ephemeral OS disks to be created for all the VMs, which don't have a cache or insufficient cache (such as Dav3, Dav4, Eav4, and Eav3) but has temp disk to store the Ephemeral OS disk.
+This feature enables Ephemeral OS disks to be created for all the VMs, which don't have cache or have insufficient cache (such as Dav3, Dav4, Eav4, and Eav3) but has sufficient temp disk to host the Ephemeral OS disk.
 [DiffDiskPlacement](/rest/api/compute/virtualmachines/list#diffdiskplacement) is the new property that can be used to specify where you want to place the Ephemeral OS disk. 
 With this feature, when a Windows VM is provisioned, we configure the pagefile to be located on the OS Disk.
 
-## PowerShell
-To use an ephemeral disk for a PowerShell VM deployment, use [Set-AzVMOSDisk](/powershell/module/az.compute/set-azvmosdisk) in your VM configuration. Set the `-DiffDiskSetting` to `Local` and `-Caching` to `ReadOnly`.     
-```powershell
-Set-AzVMOSDisk -DiffDiskSetting Local -Caching ReadOnly
-```
-For scale set deployments, use the [Set-AzVmssStorageProfile](/powershell/module/az.compute/set-azvmssstorageprofile) cmdlet in your configuration. Set the `-DiffDiskSetting` to `Local` and `-Caching` to `ReadOnly`.
-
-```powershell
-Set-AzVmssStorageProfile -DiffDiskSetting Local -OsDiskCaching ReadOnly
-```
-
-## CLI
-
-To use an ephemeral disk for a CLI VM deployment, set the `--ephemeral-os-disk` parameter in [az vm create](/cli/azure/vm#az_vm_create) to `true` and the `--os-disk-caching` parameter to `ReadOnly`.
-
-```azurecli-interactive
-az vm create \
-  --resource-group myResourceGroup \
-  --name myVM \
-  --image UbuntuLTS \
-  --ephemeral-os-disk true \
-  --os-disk-caching ReadOnly \
-  --admin-username azureuser \
-  --generate-ssh-keys
-```
-
-For scale sets, you use the same `--ephemeral-os-disk true` parameter for [az-vmss-create](/cli/azure/vmss#az_vmss_create) and set the `--os-disk-caching` parameter to `ReadOnly`.
-
 ## Portal
 
 In the Azure portal, you can choose to use ephemeral disks when deploying a virtual machine or virtual machine scale sets by opening the **Advanced** section of the **Disks** tab. For choosing placement of Ephemeral OS disk, select **OS cache placement** or **Temp disk placement**.
 
 ![Screenshot showing the radio button for choosing to use an ephemeral OS disk](./media/virtual-machines-common-ephemeral/ephemeral-portal-temp.png)
+ 
 
 If the option for using an ephemeral disk or OS cache placement or Temp disk placement is greyed out, you might have selected a VM size that doesn't have a cache/temp size larger than the OS image or that doesn't support Premium storage. Go back to the **Basics** page and try choosing another VM size.
 
-
 ## Scale set template deployment  
 The process to create a scale set that uses an ephemeral OS disk is to add the `diffDiskSettings` property to the 
 `Microsoft.Compute/virtualMachineScaleSets/virtualMachineProfile` resource type in the template. Also, the caching policy must be set to `ReadOnly` for the ephemeral OS disk. placement can be changed to `CacheDisk` for OS cache disk placement.
 
-
 ```json
 { 
   "type": "Microsoft.Compute/virtualMachineScaleSets", 
@@ -184,6 +152,35 @@ You can deploy a VM with an ephemeral OS disk using a template. The process to c
  } 
 ```
 
+> [!NOTE] Ephemeral OS disk placement option (VM cache disk or VM temp/resource disk) is coming soon on PowerShell and CLI
+
+## PowerShell
+To use an ephemeral disk for a PowerShell VM deployment, use [Set-AzVMOSDisk](/powershell/module/az.compute/set-azvmosdisk) in your VM configuration. Set the `-DiffDiskSetting` to `Local` and `-Caching` to `ReadOnly`.     
+```powershell
+Set-AzVMOSDisk -DiffDiskSetting Local -Caching ReadOnly
+```
+For scale set deployments, use the [Set-AzVmssStorageProfile](/powershell/module/az.compute/set-azvmssstorageprofile) cmdlet in your configuration. Set the `-DiffDiskSetting` to `Local` and `-Caching` to `ReadOnly`.
+
+```powershell
+Set-AzVmssStorageProfile -DiffDiskSetting Local -OsDiskCaching ReadOnly
+```
+
+## CLI
+
+To use an ephemeral disk for a CLI VM deployment, set the `--ephemeral-os-disk` parameter in [az vm create](/cli/azure/vm#az_vm_create) to `true` and the `--os-disk-caching` parameter to `ReadOnly`.
+
+```azurecli-interactive
+az vm create \
+  --resource-group myResourceGroup \
+  --name myVM \
+  --image UbuntuLTS \
+  --ephemeral-os-disk true \
+  --os-disk-caching ReadOnly \
+  --admin-username azureuser \
+  --generate-ssh-keys
+```
+
+For scale sets, you use the same `--ephemeral-os-disk true` parameter for [az-vmss-create](/cli/azure/vmss#az_vmss_create) and set the `--os-disk-caching` parameter to `ReadOnly`.
 
 ## Reimage a VM using REST
 You can reimage a Virtual Machine instance with ephemeral OS disk using REST API as described below and via Azure portal by going to Overview pane of the VM. For scale sets, reimaging is already available through PowerShell, CLI, and the portal.
@@ -197,15 +194,23 @@ id}/resourceGroups/{rgName}/providers/Microsoft.Compute/VirtualMachines/{vmName}
 
 **Q: What is the size of the local OS Disks?**
 
-A: We support platform and custom images, up to the VM cache size, where all read/writes to the OS disk will be local on the same node as the Virtual Machine. 
+A: We support platform, Shared Image Gallery, and custom images, up to the VM cache size with OS cache placement and up to Temp disk size with Temp disk placement, where all read/writes to the OS disk will be local on the same node as the Virtual Machine. 
 
 **Q: Can the ephemeral OS disk be resized?**
 
 A: No, once the ephemeral OS disk is provisioned, the OS disk cannot be resized. 
 
 **Q: Can the ephemeral OS disk placement be modified after creation of VM?**
 
-A: No, once the ephemeral OS disk is provisioned, the OS disk placement cannot be changed. But the VM can be recreated via ARM template deployment/PowerShell/CLI by updating the OS disk placement of choosing. Resulting in the recreation of the VM with Data on the OS disk deleted and OS is reprovisioned.
+A: No, once the ephemeral OS disk is provisioned, the OS disk placement cannot be changed. But the VM can be recreated via ARM template deployment/PowerShell/CLI by updating the OS disk placement of choosing. This would result in the recreation of the VM with Data on the OS disk deleted and OS is reprovisioned.
+
+**Q: Is there any Temp disk created if image size equals to Temp disk size of VM size selected?**
+
+A: No, in that case, there won't be any Temp disk drive created.
+
+**Q: Are Ephemeral OS disks supported on low-priority VMs and Spot VMs?**
+
+A: Yes. There is no option of Stop-Deallocate for Ephemeral VMs, rather users need to Delete instead of deallocating them.
 
 **Q: Can I attach a Managed Disks to an Ephemeral VM?**
 
@@ -215,7 +220,7 @@ A: Yes, you can attach a managed data disk to a VM that uses an ephemeral OS dis
 
 A: No, most Premium Storage VM sizes are supported (DS, ES, FS, GS, M, etc.). To know whether a particular VM size supports ephemeral OS disks, you can:
 
-Call the `Get-AzComputeResourceSku` PowerShell cmdlet
+Call `Get-AzComputeResourceSku` PowerShell cmdlet
 ```azurepowershell-interactive
  
 $vmSizes=Get-AzComputeResourceSku | where{$_.ResourceType -eq 'virtualMachines' -and $_.Locations.Contains('CentralUSEUAP')} 
diff --git a/articles/virtual-machines/msv2-mdsv2-series.md b/articles/virtual-machines/msv2-mdsv2-series.md
@@ -27,7 +27,7 @@ The Msv2 and Mdsv2 Medium Memory VM Series features Intel® Xeon® Platinum 8280
 [VM Generation Support](generation-2.md): Generation 2<br>
 [Write Accelerator](./how-to-enable-write-accelerator.md): Supported<br>
 [Accelerated Networking](../virtual-network/create-vm-accelerated-networking-cli.md): Supported<br>
-[Ephemeral OS Disks](ephemeral-os-disks.md): Supported <br>
+[Ephemeral OS Disks](ephemeral-os-disks.md): Supported for Mdsv2 <br>
 <br>
  
 ## Msv2 Medium Memory Diskless 
