You were right. I updated to the new firmware (with flashall, reboot ota wouldn't do) and now I have 1.4 GB.
Still, I would like to know how to access to the partition /dev/mmcblk0p10, which appears to have the other half of the space available in the Edison. It says it's mounted to /home. Does that mean that any files/SW I install there would use that space and not the one in dev/root? (I'm kind of newbie in Linux....)
The partition /dev/mmcblk0p10 is the one used for the storage of data. For example if you download files to the board you will see the changees in the space of the partition. The partition /dev/root is the one used when you install applications, packages...
In case of MariaDB you should install MariaDB's executable files into the root partition.
Then you create a data folder in /home, for example, /home/mariadb, and in the config file my.cnf point the parameter datadir to it:
datadir = /home/mariadb
If you reinstall the OS, you don't overwrite the /home partition, and the data is safe.