About of "cache=none" in PVE

Hi People

I want to do a question to somebody that know too about of caches in QEMU or to developers PVE team

The question is based in how QEMU manages the write cache when this is activated in mode "cache=none"?.

Based on this link:
http://pic.dhe.ibm.com/infocenter/ln...guestcache.htm

And this link:
http://www.ilsistemista.net/index.ph...2.html?start=2

I understand that the write cache is only in the buffer volatile of the RAID controller or in his default in the buffer volatile of same HDD (if we don't have a RAID controller). So if we have a RAID controller with BBU, we will not should worry for the lost of data.

But many people said me that QEMU with the option "cache=none" enabled, his write cache is in RAM of Host or Guest.

Is correct this?, and
What options of QEMU can I use for get this behavior (write cache should be only on the buffer of the RAID controller/Disk and not in the RAM of Host/Guest)?

Best regards
Cesar