I'm trying to understand how ILM works with the default 50GB/30days policy if I also want to move indicies longer than 7 days to warm nodes and it takes longer than 7 days to fill an index. Should I actually be making the rollover policy 50GB/7days to match the move to the warm tier? I originally had it like this but it resulted in more open indicies and more memory usage so swapped it back. I don't believe I can then merge multiple 7 day indicies after they've left the hot tier either? Any guidance would be appreciated. Thanks.
From the docs;
Rolls over a target to a new index when the existing index meets one or more of the rollover conditions.
So that means if the index is 5GB and 7 days old, it'll still rollover, ie the conditions are the max values of whatever you define.
Basically you need to make a call on if the 7 day limit, or the 50GB size is the more important.