Keeping data with max available expiration and performance concerns


I develop my metrics based on influxdb. I want to keep the data forever therefore my retention policy is set to inf and my shard retention policy is set to 100 years (the max I could set).

My main concern has to do with degrading performance by keeping this data. My series will not be more than 100000 (as adviced for the low server specs).
Is there gonna be an impact on the memory used indexing wise? More specific memory used by influxdb regardless of issuing any actions such as queries/continoues queries
Also in case there is a problem with performance, is it possible to backup only the data that are bound to be deleted?

Kind Regards!