I am using Ubuntu 14.04. Did the upgrade few months ago. My system was working normally until yesterday it started lagging. The system frequently hangs for 30 seconds (approx or more than that), and there is lagging response as I type. Other than that system is working normal.
I googled for this and found this answer: https://askubuntu.com/a/21643/55026. Third point helped me and I am getting these messages from kern.log
Jul 4 16:11:40 moony kernel: [24200.058787] ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
Jul 4 16:11:40 moony kernel: [24200.058792] ata1.00: failed command: FLUSH CACHE EXT
Jul 4 16:11:40 moony kernel: [24200.058796] ata1.00: cmd ea/00:00:00:00:00/00:00:00:00:00/a0 tag 0
Jul 4 16:11:40 moony kernel: [24200.058796] res 40/00:00:00:4f:c2/00:00:00:00:00/00 Emask 0x4 (timeout)
Jul 4 16:11:40 moony kernel: [24200.058797] ata1.00: status: { DRDY }
Jul 4 16:11:40 moony kernel: [24200.058801] ata1: hard resetting link
Jul 4 16:11:45 moony kernel: [24205.432930] ata1: link is slow to respond, please be patient (ready=0)
Jul 4 16:11:45 moony kernel: [24205.488995] ata1: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
Jul 4 16:11:45 moony kernel: [24205.490405] ata1.00: configured for UDMA/100
Jul 4 16:11:45 moony kernel: [24205.490412] ata1.00: retrying FLUSH 0xea Emask 0x4
Jul 4 16:11:45 moony kernel: [24205.504962] ata1.00: device reported invalid CHS sector 0
Jul 4 16:11:45 moony kernel: [24205.504981] ata1: EH complete
System details:
HDD - 500GB TOSHIBA MK5076GS
RAM - 4GB DDR3 in two slots
CPU - Intel(R) Core(TM) i5-3210M CPU @ 2.50GHz
Display - 3rd Gen Core processor Graphics Controller
Laptop - HP 2116TU
I have googled the error messages and they say that it might be some hard disk problem.
UPDATE: System used to hang while copying large file (movies, etc.) to system. But I used to ignore them.
