Surprisingly Slow Random I/O on UTM

[d-shehu]

I did some quick searching on the forum and Googling but I couldn't find the info. I've got a Macbook M3 Pro I've been using with Apple virtualization (not emulated).

I have this odd use case for using VM within a VM and happened to notice random disk i/o was extremely slow. I'm storing the UTM VM on portable SSD. I tested with fio by running the same 4 tests on the Mac, outer and inner VM (same drive). I understand there's significant overhead even with virtualization but the drop off from host to the outer VM seems crazy.

Am I missing something? Most of my virtualization is within Ubuntu (KVM/QEMU) or Proxmox. I'm pretty sure nested virtualization is enabled. Same deal on Intel Macbook Pro.

Sorry if this was addressed already and thanks in advance.

Test	macOS (bare metal)	(outer VM)	(inner vm)
Sequential read	3165 MB/s	2279 MB/s	1193 MB/s
Sequential write	2394 MB/s	2006 MB/s	1160 MB/s
Random read	754 MB/s	55.8 MB/s	23.9 MB/s
Random write	138 MB/s	19.8 MB/s	9.79 MB/s