On Tue, Aug 12, 2025 at 03:53:54PM +0800, Chao Yu wrote: > > What did you use before? At least for older qemu the default was > > buffered I/O, which can lead to very expensive fua or flush calls. > > Previously, I didn't use any cache= option, as manual described, it > should equal to cache=wrteback. Modern qemu actually split the cache option. You absolute want cache.direct=on. If you don't do simulated power fail testing by killing qemu (or run real workloads for the matter, but who does that :)) it might make sense to just ignore the flushes with cache.no-flush=on as well, which is what I do for my test VMs on the laptop.
