I have two identical linux boxes (running ubuntu 13.4) with identical hardware including a WDC WD20EARS hard disk. I noticed that my main system got unsually slow and performed a number of HD tests. SMART did not look suspicious and gave nearly identical results on the two machines.
There is one test where I see a big difference, though, and this is HD speed test by hdparm. On the problematic machine, I get
> sudo hdparm -Tt /dev/sda /dev/sda: Timing cached reads: 24876 MB in 2.00 seconds = 12450.96 MB/sec Timing buffered disk reads: 26 MB in 3.18 seconds = 8.18 MB/sec
while on the other (identical) machine I get
> sudo hdparm -Tt /dev/sda /dev/sda: Timing cached reads: 29000 MB in 2.00 seconds = 14515.76 MB/sec Timing buffered disk reads: 348 MB in 3.01 seconds = 115.56 MB/sec
I tested this several times on otherwise idle machines, but the big difference in 'buffered disk reads' persists.
Any idea what might be causing this and what can be done about it? I also had a look at the diagnostic hdparm output but did not get any clues from that because both machines produced identical output. The machines are about 1 year old and have 16GB memory.
any hint would be appreciated - Many thanks in advance