There are some tricky and unclear things in Firebird, which do not affect the performance or reliability, but they are curious. Some of them we are going to show, but not explain.
Let's start with restore sizes.
Grab any real-life Firebird database you have (but not an employee.fdb, it will not work with it).
Make a backup.
Then make restore with gbak using only param -c
gbak -c ...
after that make restore to the different database with -v[erbose] output param which make verbose output during restore:
gbak -c -v ...
then take a look at sizes of restored databases.
Are they identical? Usually you can see difference in sizes, equal to 2 database pages. Why turning on verbose output makes such difference? Well, nobody knows :)
Go Firebird! Have a good week-end!