Snapshots and Rollovers (Data duplication?)

Hey all,

We’re looking at setting up snapshot policies for our indexes, and wanted to understand how the underlying data is handled when we’re doing periodic rollovers.

I understand that snapshots are incremental, so if we expand an index, a subsequent snapshot will only included the changes since.

However, if we are rolling over the index, and a snapshot happens before and after rollover, how is that handled? Does the same underlying data get duplicated because those are two distinct indexes? We change the number of shards / replications, and move the shards during rollover.

Cheers!