Is possible to use an internal HDD with 2tb then? I read that maximum capacity that is compatible with ps3 is 1.5 tb
man... so it is impossible

So, the guide goes something like this:
1. You need to download the Seatools Bootable image from the Seagate offsite.
2. Upload image to flash drive
3. Boot from a flash drive on a computer, connect HDD 2.5" 2-3TB via USB
4. Select Advanced mode by pressing F8.
5. Press Advanced again, select "Set LBA", then F8 to continue.
6. Set LBA value to 3221225471 (maximum LBA value supported by PS3)
If there is at least 1 more, then everything is gone.
7. Install HDD 2.5" 2-3TB in PS3, format.
At the end of the process, PS3 will show a capacity of 1366GB free / 1536GB total (part of the disk space is reserved for the needs of PS3).