The InnoDB redo log consists of a list of files that logically form
a bigger file, as if the individual files were concatenated together.

The first file will always be written on redo log checkpoint, because
the two checkpoint pages are at the start of the single logical
redo log file.

There is no technical reason why InnoDB requires at least 2 files
to exist. Let us reduce the minimum number to 1. In that way,
restoring from backups will become easier, since InnoDB can directly
deal with a single backed-up redo log file.