look there:https://github.com/odoo/odoo/issues/2811

odony commented on 7 Oct 2014

For the record, some clarifications:

In Odoo 8 the system parameter (ir_attachment.location) is still supported, but it is only used to switch between file-storage and db-storage, not for selecting the location (for security reasons, see below). It defaults to file-storage, as explained previously.

The filestore location can only be controlled via the configuration file (data_dir), not via the database, for security purposes. Otherwise external users might trick the system into reading arbitrary files. It defaults to a platform-specific location inside the home directory of the user executing the service.

The 'Attachments' menu only appears when the Document module is installed (this was already the case in 7.0). If you do not install it, attachments are only available as part of the message history under most documents.

The backup format has been changed to be a Zip archive containing both a database dump and a copy of the filestore. During a restore it will be extracted and copied back into the filesystem. This does not mean that taking backups will move your filestore into the database, it only means that the filestore is backed up and restored along with the database contents.

Attachments are stored in <root directory of odoo>/.local/filestore

all the files are renamed using encryption so that there are no duplicate files

If I have a clean instalation and I want to know where are the attachements going to be stored what I should do?

attachments are going to be saved in the filesyste, under home directory of user running the odoo instance (for example: "home_dir_path/.local/share/Odoo/filestore/db_name/..."), whereas files are not saved with original names, but file names are always saved in the database. so you can NOT find a file by name in the filesystem, but actually they are there. for more details, you can refer to my answer here.

It is true that the default mode of saving the binary attachments is inside filestore, and not in db?

yes.