Hello, Hugo!

Thursday, June 27, 2013, 1:28:18 AM, you wrote:

HE> My database size: 4 GB

I doubt to use nbackup for that size of database. because usual
gbak -b -g must take around 5 minutes, not more.
Restore of that db also must take around 15 minutes.
And, the timing I mention is for cheap SATA II drives (1 for db and 1
for backup), not for cool RAID storage, or even for SSD - there
usual backup and restore speed will be like lightning.

You may start to think about nbackup when your db will reach ~20gb
size.

HE> Could you help me with the nbackup?
HE> What the best use? Keys, frequency, etc...
HE> How to restore?

read
http://www.firebirdsql.org/manual//nbackup.html
as many times, until you will understand it.

nbackup -b 0
is kinda file copy, with the near same speed
nbackup with higher levels will read whole db, but write only changes,
so, it is faster.
But, if you use Classic, consider not to use nbackup with Firebird
less than 2.5.2 (or even 2.5.3).

--
Dmitry Kuzmenko, www.ib-aid.com