In some scenarios, you may need to move a disk from IDE to SCSI bus or vice versa. Sample scenarios include but are not limited to:
VM does not boot due to missing SCSI driver. In such cases, the disk can be converted to IDE to install the missing drivers and then moved back to SCSI.
A wrong disk type was used during VM creation.
Application requirements dictate the particular type of the disk.
You have recently migrated VMs to AHV and noticed that some of the disks appear in IDE format.
After following the disks conversion process from IDE to SCSI (as described in step 2 of the uvm_ide_disk_check) the following doubts arise:
Question: Once the disk gets converted, does it immediately redirect all I/O to the SCSI drive and leave the IDE disk unused?
Answer: Once the conversion is completed (which is actually a cloning process from the original IDE disk), the new SCSI disk needs to be attached to the SCSI bus and then the old IDE disk could be removed.
Question: What are the risks associated with running the conversion process on a live system?
Answer: Since the conversion process is based on the cloning to ensure the data is identical it is recommended to power off the VM since the live system will generate I/O to the disk.
Question: Is there any limit as to how long an IDE disk can remain on the VM before being deleted? Will it have disk space implications?
Answer: There is no limit as to how long an IDE disk is kept before being deleted. If the IDE disk is not being used for new data, there should not be any space issues.
There is a post you can consult that talks about how to convert IDE disks to SCSI :
More about the common VM disk management workflows, check out: AHV | Common VM disk management workflows