Inconsistency with respect to volume size and disk offerings

### The required feature described as a wish

ISSUE TYPE

Enhacement/Bug

COMPONENT NAME

Component: Enhancement/Bug

CLOUDSTACK VERSION

Cloudstack version 4.20.x

SUMMARY

Inconsistency with respect to volume size and disk offerings

As this could cause usage issue for the operator

**Steps to reproduce the issue**

Following are the scnearios where there is a mismatch between volume size and its associated disk offerings.

This could cause usage issues for the cloud operator

Scenario1

1. Use or create a diskoffering disk which has "Disk size strictness" as false and a fixed Disk size

2. Deploy a vm with a data disk offering, let's say using the default Small disk offering ( 5gb)

3. Stop the vm

4. Change the disk offering to Medium API using tha api or the UI

https://cloudstack.apache.org/api/apidocs-4.21/apis/changeOfferingForVolume.html

(changeOfferingForVolume)

5. The data disk volume size changes to 20 gb

6. Disk offering remains Small

Scenario2

1. Create compute offering with "Disk offering strictness" set true

Screenshot

Let's say small disk offfering

2. Launch a vm with root disk

3. Stop the vm

4. Resize of the root volume to 10 gb

Scenario 3

1. Create a disk offering with "Disk size strictness" true on shared storage ( say 10gb)

2. Deploy a vm with data disk on the shareed storage

3. Stop the vm

4. Migrate the data disk volume to local storage and replace disk offering to a local disk offering ( of size 20gb)

5. Size of the disk remains 10gb but the offering is differnnet

Screenshot

Current behaviour

The Inconsistency can be reduced when the user applies the following configuration

Create a root disk with Disk offering strictness

Create a data disk with Disk size strictness"

Enhacement request

Introduce a global parameter to disable the resize operation for any volume

Introduce the Disk offering strictness option to disk offerings also,

Currently its only available for compute offerings

Start with the changeOfferingForVolume API and reproduce the three reported scenarios in CloudStack 4.20.x, including disk-size strictness and storage migration. Compare the resulting volume sizes and disk offerings, then define how the proposed global resize restriction and disk-offering strictness should behave across these cases.

Written by the indexing model from the issue text.