MariaDB comes with support for additional storage engines such as XtradB, Aria including the other storage engines such as Innodb and MyISAM. You will find more details here :
https://mariadb.com/kb/en/mariadb/choosing-the-right-storage-engine/
PAM is an authentication plugin supported by MariaDB.
[FONT="]PAM is short for [/FONT]Pluggable Authentication Modules
[FONT="] and is an authentication framework used by Linux, FreeBSD, Solaris, and other operating systems. It is not supported on Windows servers.
[/FONT]PAM makes it possible to implement various authentication scenarios of different complexity. For example,
authentication using passwords from /etc/shadow (indeed, this is what PAM usually does for a normal shell logins, for pop3, imap, and many other services)
authentication using LDAP
authentication using ssh passphrases
authentication using one-time passwords (even with SMS confirmation!)
combining different authentication modules, where either one or all of them are required to succeed
password expiration
user name mapping
limiting access by time, date, day of the week, etc.
logging every login attempt
and so on, the list is in no way exhaustive.
Which version of Mysql are you using?
Databases on Mysql 5.6 are compatible with MariaDB and can be safely upgraded. But as I mentioned earlier, it is a non-reversible process, so make sure to take a full backup of all your mysql databases prior to upgrade.