Caching modes in QEMU
| Mode | Host page cache | Guest disk write cache |
|---|---|---|
| none | off | on |
| writethrough | on | off |
| writeback | on | on |
| unsafe | on | ignored |
Considerations
- device.virtio-disk0.config-wce=off (qemu) or config-wce=off (libvirt) prevents guest from setting the write cache
- Use cache=none for local RAW storage, cache=writethrough for NFS/iSCSI backed storage