Help, 250% Hard Drive Write Speed Decrease

[itachi737]

Hello,

 

I tried copying 1.9TB worth of videos from my 3TB  3.5" Seagate Barracude 7200rmp drive to my 6TB  3.5" Seagate Archive HDD v2 (ST6000AS0002) 5900 rpm drive. I am using Ubuntu 16.04, both drives are formatted in ext4, the 3TB one is connected internally via sata 3 and the 6TB one over usb 3.0. The video files are between 300MB and 3GB. At first everything went fine. I was getting  a transfer speed of 130MB/s. I left the house when it had transferred around 200GB. When I came back it was transferring at 46MB/s. Since then I can't get it to write above 50MB/s regardless of what I try to copy.  I also tried copying from the 6TB drive to the ssd where to os is installed and the max I get is 65MB/s, so the read speeds are also extremely low. I used a bunch of 5GB video files to make sure that I'm getting optimal speeds (though if I am not wrong 300MB, which is the size of the smallest video I have, should also be good enough). When I do the benchmarks with the disk utility provided by Ubuntu it get normal speeds or at least I believe they are normal. (see results below). So my question are : Does anybody know what is causing this decrease in performance? Is it normal? If it is not how can I fix it?

 

I read only a bunch of forum posts and articles only. I understand that the drives get slower the more you fill them, but from what they were saying you start to see a drastic decrease in performance once the drive is 85% full, but mine is not even half full (1.9TB / 5.6TB).

 

Benchmarks: access time 13.63ms

A) at 1MiB    21MB write and 63MB read      B) at 10MiB    46.5 write and 125MB read      C) at 100MiB     113.4MB write and 134.5MB read      D) at 500Mib   134.4MB write and 138.5MB read

 

 

Thank You