ubuntu 14.04 periodically becomes VERY slow

[silver.bullet at zoho.com]

On Mon, 31 Aug 2015 16:54:51 +0200, Oliver Grawert wrote:
>the "grey-out feature" of unity clearly points to either your CPU being
>under high load or your disk not being able to deliver data at the
>expected speed (I/O issue).

http://bencane.com/2012/08/06/troubleshooting-high-io-wait-in-linux/

$ sudo -i
# for i in 1 2 3 4; do hdparm -tT /dev/sda; done