※This sample exam is different from those that appear in the actual OSS-DB Exam.
There are various ways to back up the database. Physically copying all the files in the directory of the database cluster is the most fundamental backup method, but since the database must be stopped, whether it is practical or not depends on environmental restrictions.
Database clusters are incompatible between major versions. For example, if you copy files of 9.1 database cluster and restore to 9.2 environment, it can not be used.
Also, with this method you need to back up the entire database cluster and you can not retrieve and copy only some tables.
Compared to logical backup by pg_dump, simple file copy is generally faster because pg_dump needs to read the file, extract its contents and output it. However, since pg_dump does not output the contents of the index etc., the file copy will be larger in size.
Therefore, the correct answer is C.