As I known, the first snapshot backup after creating repo is full backup, after that, it's incremental by default. But it seems there is no way to set the mode manually. Is there any one has the experience, please share, thanks.
You cannot, you need to create a new repo for a full backup.
yes, I think no before my ask.
Why, is it a fundamental feature for ES backup?
Because it isn't needed.
Incremental backups are only incremental in that they don't re-copy files that haven't changed in the index. Since the index is mostly write once this works out fairly well.
You don't need to keep the old backups around though. Deleting the old backup will only remove files that aren't needed to restore any existing backups. It works like a reference counting garbage collector.
Thank you for your reply
As your said, how I could control backup data size? The storage is not free for my case.
My planned strategy is to keep backup data in latest 7 days, it seems not possible, right??
The only knob you have to control size is deleting old backups. Deleting
old backups will remove whatever files are no longer needed. The files
don't stick around forever.