Too much RAM and another issue (8 replies)

Hello Community,

i have 2 little problems and hope u could help me.
i have a debian 6 x86 vserver with 756mb RAM
[spoiler]
root@vserver:/tmp# uname -a
Linux myhostname 2.6.32-6-pve #1 SMP Tue Sep 13 10:44:10 CEST 2011 i686 GNU/Linux
[/spoiler]

but mysql uses really too much RAM:
[with MySQL:]
root@vserver:/tmp# free -m
total used free shared buffers cached
769 483 285 0 0 483
_
[without MySQL:]

root@vserver:/tmp# free -m
total used free shared buffers cached
769 171 597 0 0 171


If i am under a DDos attack 285MB free MB RAM is not enough.
Since yesterday 400MB were free.

The second issue is that i wanted to use MyISAM.
i use vbulletin as forum system. And in my opinion it works better with MyISAM as Inno.

Here are my configs:
1. mysql> show engine innodb status\G; :
http://nopaste.me/paste/1262042168500fb946ed8a1
2. /etc/mysql/my.cnf:
http://nopaste.me/paste/655069022500fb98fe0d8b

Pls don't forget that i am a newbie ;)

thanks a lot