Thatks for your answer @bigpup :
1.- There is enough space to copy the back up ( I tried with the default option and then I tried with other disks just to try... and nothing happened)
2,. The partition has the same format as the instalation...I made backups there before and there was no problem.
3.- I tried to copy directly the save file (.4fs) starting with other puppy linux distribution, and I cant copy it, it said... CAN SPLIT FILE... and the copy process finished.
I don't know where the problem is.... I tried a lot of things (changing the destination folder to other partition, to other disk , to usb, to external disk, to... but there is no solution) , it star copying the .4fs but when it copied about 400 Mb it says there is an error.
I don't know what happens
I can work with my distro, but i can't make a security copy,... so ¿=¿=??=
----edited.------
When I made a security copy compressed, it made it (I don't know if it works or not, but it finished the compressed copy with no problems.....)
My puppy is configured the way I want, so there is no real need t o make a backup, but I like to be prepared to future problems... haha)