My customer asked to create a solution for backing up his Firebird database. I have developed a solution using nbackup and send a tar bz2 file of the NBK to an S3 bucket in the Amazon. The database file size is huge as 56Gb. Is there any limitation of Firebird as the size of the database increase? any suggestion for improve this scenario?

CentOS release 5.7 (Final)
Firebird TCP/IP server version LI-V2.5.2.26540 Firebird 2.5
Physical Backup Manager version LI-V2.5.2.26540 Firebird 2.5