Hi, Im not sure if this is correct forum.. but. Sometimes my macbook 17'' 2011 is lagging, freezing. I have always eye for memory/cpu usage (iStat), so I see I always have at least 1-2GB ram free (of 8GB total), cpu usage is very rare more than 20%. Maybe it's lagging because of iowait? There's some good way to find out what is causing slowness sometimes? If I will know that this is hard drive for example I can buy ssd. But I'd like to know before I'll buy anything Thanks!