Help for explication backup and storage

[Schinas Florian]

Hi all,

Well, I 'm currently working on the backups of MySQL Cluster .

However I'm pretty lost and I 'd like a certainty from you.

To make a backup of the cluster , use the command " START BACKUP" .
To restore it you must use the program " ndb_restore " after emptying the storage nodes.
I know that "START BACKUP" creates three files :
CTL
LOG
DATA

But I 'd like to know , that it contains they?
Despite the use of MySQL Cluster , my MySQL nodes , I still have the files of database / tables that are created , so, why MySQL Cluster is said that stores all the storage nodes in RAM ?

Should , in addition to backup MySQL Cluster with "START BACKUP" to backup the MySQL server with the command " mysqldump " and restore simultaneously LIVE BACKUP MySQL Cluster ?

Thank you for your help and answer!
Best Regards,

Florian