Hi… You might be thinking of / remembering the LiteVFS (with the “V”) sub-project:
There was only a single post about it, that I recall, and presumably the sunsetting of LiteFS Cloud means that a non-trivial restructuring would have been needed, even if it was still active…
Regarding the broader question about volumes…
It should be possible via “process groups”—namely having the primary-candidates in one group and everything else in the other. The [mounts] section of fly.toml should allow the restriction of the volumes to the first.
That may not be wise with the usual LiteFS (without the “V” now), although I have to admit that I’m slightly tempted to try it out myself now, with a throwaway cluster…