If the memory recycling mechanism is set up, old data will indeed be deleted when the memory is full. In this way, when persisting again, the corresponding persistent data in the disk will also be deleted. But persistence only refers to writing data from memory to disk. For example, when data is stored in MySQL, we will also call it persistence. But after you delete a piece of data in the database, there will be one less record in the database. .
In addition, Redis persistence should not provide query functions, which means that if the memory cannot be found, check the disk. Persistent data will be synchronized to the memory. If it does not exist in the memory, it should theoretically not exist on the disk.
I have answered your original post. You should be able to understand the link attached if you go in and take a closer look.