I put one below comparing native WSL FS to virtiofs. 50s build time on native vs 75s build time on virtiofs. Virtiofs came to about 50% slower, and likely only 25% slower than native (i saw MS defender kick in, which you can disable). The older “plan9” aka “9p” is likely 10x slower. I don’t use plan9 (the current windows file system in WSL), but I would guess that same build would take 3-5m or more.