Data loss caused when stopping and starting a VM instance on GCP?

1
votes

NOOB alert I received a recommendation in GCP stating that an instance has had low CPU utilization recently and I should consider switching to a lesser powered machine type. When trying to do this downgrade, I'm shown the following warning:

To change the machine type, Compute Engine needs to stop and start this VM > instance. Stopping and starting the machine may cause resources, such as local SSDs and ephemeral IP addresses, to be lost.

I need to know what kind of data loss there might be? We have some software/data-files on the machine that we don't want to loose. If this has to be done how can we backup this data?

Also is it possible to avoid the change in IP address?

1
google-cloud-platformgoogle-compute-engine
CPU Utilization is just one metric used to size a Compute Engine VM instance. The smaller the instance size the lower the allocated Memory, Disk IOPS and Networking bandwidth. I have lots of instances with 5% or less CPU but I require bandwidth for IOPS and networking. Consider all factors before changing the instance size. – John Hanley

1 Answers

4
votes

A compute engine may have a variety of different storage devices attached to it on which file systems may be created. Specifically, there are three primary types:

  1. Persisent disk - standard hard-disk (platters). Exists as NAS storage.
  2. Persistent SSD - SSD disks (solid state). Exists as NAS storage.
  3. Local SSD - SSD disks (solid state). Exists as directly (physically) attached storage.

"Local SSDs" do not survive moving the machine from one physical environment to another. You should examine your compute engine and see what storage types you are using. Local SSD is not any kind of a default and you would have had to explicitly add it if you are using it.

If your compute engine is to appear on the Internet, it will have an Internet IP address. There are two choices for this IP.

  1. Ephemeral IP - An IP address that is dynamically assigned by Google from a pool and allocated to your compute engine. Not assured to be yours forever.
  2. Static IP - An IP address that is dynamically assigned by Google but is associated with your compute engine until explicitly released.

There is no charge for usage of a Static IP address associated with a compute engine while the engine is running ... but you are charged 1 cent/hour if you have a static IP address and the compute engine is not running.