Azure VM升级或降级停机时间

Question

It's my first time using Azure and I am so used to AWS. In AWS when you downgrade or upgrade your instance, a downtime is expected.. In Azure documentation there is no downtime specified when upgrading or downgrading a VM, does that mean that there is no downtime? If there is, how long is the downtime?

Answer 1

In Azure, there are two types of Microsoft Azure platform events that can affect the availability of your virtual machines: planned maintenance and unplanned maintenance.
To reduce the impact of downtime due to one or more of these events, we recommend the following high availability best practices for your virtual machines:
1.Configure multiple virtual machines in an availability set for redundancy
2.Configure each application tier into separate availability sets
3.Combine a Load Balancer with availability sets
4.Use multiple storage accounts for each availability set

Note: Avoid leaving a single instance virtual machine in an availability set by itself. VMs in this configuration do not qualify for a SLA guarantee and face downtime during Azure planned maintenance events, except when a single VM is using Azure Premium Storage . For single VMs using premium storage, the Azure SLA applies.

More information about SLA for Azure VM, refer to the link .

Answer 2

There's a downtime involved. Depending on the deployment model (Resource Manager or Classic), resizing would involve either just stopping the VM (former) or deleting and recreating the VM with new size (latter).

From https://azure.microsoft.com/en-in/blog/resize-virtual-machines/ :

Resize Resource Manager (ARM) virtual machine s

If your VM(s) are deployed using the Resource Manager (ARM) deployment model you can resize VMs by first stopping your VM, selecting a new VM size and then restarting the VM . If the VM you wish to resize is part of an availability set, then you must stop all VMs in the availability set before changing the size of any VM in the availability set.

Resize classic (ASM) virtual machines

Resizing a VM deployed using Classic (ASM) deployment model is more difficult if the new size is not supported by the hardware cluster where the VM is currently deployed. Unlike VMs deployed through the Azure Resource Manager deployment model it is not possible to resize the VM while the VM is in a stopped state. So for VMs using the classic deployment model the VMs must be deleted and then recreated using the same OS and data disks .

Answer 3

Whether you can shut down a VM or not depends on whether the new VM size you want to change is available on the existing hardware cluster and whether the VM is deployed in Availability sets.

There is a nice article here on Microsoft docs that explain when you can change size without deallocating VM and when you must deallocate VM.

In short, using Powershell you can change the size of your VM and you do not have to stop and deallocate vm if the new vm size is available on your hardware cluster.

Please note that VM still shuts down and restart as a result of the VM size update and typically takes about on an average of 2 min to get it up and running for windows VM without any customization as per my personal experience.