> I have a Firebird 2.1 database. I use gbak 1.5 version and I able to backup the database with the following command:
>
> gbak -b -v server:/data/db/mydb.fdb backup.fbk
>
> I thought Firebird 2.1 ODS is 11.1 and Firebird 1.5 is 10.1. Why the backup still success? Will I encounter any problem with the
> backup in later stage?

gbak just SELECT's the data and store it in fbk file. gbak not worked with database
file directly.

> Is there possible that gbak will fail if there are any special feature used in the firebird 2.1 database?

Yes it can fail. Old gbak can't understand new metadata features.

Regards,
Vlad