change drive cache settings without losing OS

Hi how do i change the drive’s cache type without losing the ability to boot the OS thats on it? The last time i tried it i couldnt boot the guest OS. As i’ve fixed the issue of crashes, i dont have to worry about IO so want to use the caching feature as its a big boost to the performance.

It seems that KVM has features that significantly speed up guest OS then running them natively.

You’ll need to clarify what drive cache you’re referring to…
Drives are cached a number of different ways, some in ways that are controllable by a User and others not.

And, there are configurations that affect disk caching but are not the actual caching like the disk I/O scheduler.