I'm having trouble with a couple of Seagate 4TB hard drives that seem to have inconsistent performance.
Here's the results of running hdparm -t /dev/sde four times in a row;
Timing buffered disk reads: 2 MB in 4.69 seconds = 436.56 kB/sec
Timing buffered disk reads: 2 MB in 4.70 seconds = 436.05 kB/sec
Timing buffered disk reads: 446 MB in 3.01 seconds = 148.21 MB/sec
Timing buffered disk reads: 444 MB in 3.00 seconds = 147.94 MB/sec
And the results for hdparm -t /dev/sdb;
Timing buffered disk reads: 2 MB in 4.67 seconds = 438.46 kB/sec
Timing buffered disk reads: 378 MB in 3.01 seconds = 125.77 MB/sec
Timing buffered disk reads: 372 MB in 3.01 seconds = 123.73 MB/sec
Timing buffered disk reads: 378 MB in 3.00 seconds = 125.88 MB/sec
I believe inconsistent results from hdparm are not uncommon (hence why it's worth running several times). But I'm finding the slow performance is causing buffering while trying to watch movies/tv shows from my NAS. So the issue is more significant than just some fluctuations in readings. Also, both the drives are relatively new and bought from two completely different sources and have no bad sectors. It strikes me as strangely co-incidental that they are both Seagates, though... so I'm wondering if there is some kind of factory setting I need to change. I have a 4TB Western Digital Red, and it hasn't caused me any problems.