Does Volatile Cache Contents flush *all* L2 data or only Defer write data?

[COOKIEMNSTR]

Question is the title Does turning on "Volatile cache contents" force clear the L2 cache read AND write data (essentially emptying the L2 every reboot) OR is it only flushing the Defer-Write data from cache to the source disk?

Asking because I am setting up a dual boot system where the 10tb HDD is cached in L2 mode on the primary windows install with defer-write, but when I dual-boot into the second OS, the 5TB will be accessed from time to time but the L2 cache nvme should be completely untouched.

I would prefer the behaviour to flush any leftover defer-write data that has not been written already at shutdown, but leave the read portion of the cache there between reboots.

Thanks!

[Support]

I'm sorry for the late reply. Regarding your question, this option has nothing to do with flushing deferred write-data. All deferred write-data will be flushed at the shutdown phase. This option is to reset/empty the whole L2 cache at the bootup phase.
In your case, if the 10TB HDD is not touched in your second OS, you may not check this option.