How much RAM is needed for large databases?

Question

MySQL

Good afternoon. There is a server with 32 GB of RAM on board. How many databases can support (max size) MYSQL.? Here's my stats:

• Actually, at the moment 25 databases are connected (sites on Wordpress). Used by MyISAM and InnoDB about 50/50.
  
• The total number of articles (records in the wp_post table) is 4k.
  
• In wp_postmeta tables - 6 times more, i.e. 24kk.
  
• The total sum of entries in all tables is approximately 4kk + 24kk + 3kk = 31kk
  
• The total weight of all Bases is about 80GB .
  
• Basically queries go SELECT and read .
  

After the last addition of the database to 10 GB, the Server began to slow down terribly. WA goes off scale to 80, LA 40-80. Is this normal for this size? Or is there a way to reduce the load?