I have a MySQL database running on an Ubuntu box that pings 250 clients once a minute (24x7). My column names are: `ip_address [varchar(16)], status[varchar(7)], timestamp(datetime)`. 

Been running it for several weeks and its grown (10,581,421+ rows). I run a query to return the most recent 800 results on a specific ip address:

    "SELECT * FROM (SELECT Device_ip,Status,timestamp  FROM ping_results where Device_ip = 
    '192.168.1.1' order by timestamp desc LIMIT 800)SUB ORDER BY timestamp asc"

It takes 10+ seconds to return the results. Is there anything I can do differently to speed this up?