Mass file copy speed starts fast but slows down, then fast again

Discussion in 'Windows 10' started by eemuler, Sep 23, 2019.

  1. eemuler

    eemuler MDL Senior Member

    Jul 31, 2015
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    My laptop had an M2 SSD and a SATA HDD. I bought a SATA SSD to replace the SSD. I copied everything from the HDD to an external USB drive, then physically replaced the HDD with the new SSD and formatted it using Manage-> Disk Management.

    When I copied the files I had backed up to the external USB drive back to the new SSD drive, the file copy stared off fine, but then unexpectedly slowed down after a few tens of seconds. After running at the slow speed for about a minute, it sped up again to full speed. This cycle repeated until the file transfer was finished.

    At first I thought it was the USB HDD, but then I tried with the M2 SSD. This is blazingly fast, so the problem occurs after a significant amount of data has been transferred, but it is there. Initially, the disk usage is low and the transfer speed fast, limited by the slowest disk/ interface. Then suddenly the disk usage on the internal destination disk will go to 100%, regardless of which drive it is. This causes the transfer speed to slow down to about 10 MB/s. After a while, the disk usage automatically drops to a low value and the transfer speed goes back to the previous fast speed.

    Speeds switch between two values: (ignoring the initial burst of cached speed).
    USB drive to SATA SSD: ~110 MB/s and ~10 MB/s (USB drive is HDD, so 110MB/s is good)
    M2 SSD to SATA SSD: ~500 MB/s and ~10MB/s
    USB drive to M2 SSD: ~110 MB/s and ~10 MB/s
    SATA SSD to M2 SSD: ~500 MB/s and ~10MB/s

    The new SSD in question is a Pioneer 1 TB 2.5" (APS-SL3N-1T).
     
  2. eemuler

    eemuler MDL Senior Member

    Jul 31, 2015
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    OS Windows 10 64 bit Pro Clean install 1809 upgraded to 1903.
    Laptop Clevo P957HR. i7-7700HQ 16GB GTX1070 MaxQ (8GB) - Samsung M2 960 Pro 512GB - Pioneer 1 TB 2.5" (APS-SL3N-1T).
     
  3. oilernut

    oilernut MDL Senior Member

    Jul 8, 2007
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    If you are copying a ton of small files you'll see the speed drop down significantly compared to a couple very large files.
     
  4. eemuler

    eemuler MDL Senior Member

    Jul 31, 2015
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    Fine, but why is it going up and down like a yo-yo?

    And this is happening on fairly large files.
     
  5. Enthousiast

    Enthousiast MDL Tester

    Oct 30, 2009
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    I have something like this, i had a 1TB hdd and when i tried to extract something to it or copy over a windows 10 iso, it started with 170000KByte/s and dropped very low, freezes the browser, and even needed to do a hard shutdown.

    I replaced the 1TB with a brand new 2TB hdd, and now it happens when i want to copy iso's to one of the old 2TB Enterprise hdd or the 3TB barracuda.

    I've tested the RAM with passmark memtest86, no errors.
    I checked the system ssd (samsung 850 pro 256GB, running 18362.356) with magician, reported to be good (100TBW from the 300TBW guaranteed).

    Now exchanging the system ssd with a brand new one, just to see if a new/clean install won't have these problems anymore. On this ssd i can install different win 10 releases, atm it runs 18362.10019 but will test 1809 too.

    When it also happens on the fresh installs, it can be a faulty controller, which i don't hope it is:(
     
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  6. eemuler

    eemuler MDL Senior Member

    Jul 31, 2015
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    01.png 02.png

    After a few more seconds the disk usage came down and the speed went back up.
     
  7. pf100

    pf100 MDL Expert

    Oct 22, 2010
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    Whenever I have problems with hardware I boot into another operating system to see if it does the same thing. If it does, it's the hardware.

    A good example would be a usb problem on a laptop I worked on earlier today. With Windows 10 LTSC I could read from a usb flash drive just fine. If I tried to write to any usb flash drive it would fail after a few hundred megabytes every time.

    I made a bootable linux usb flash drive, booted linux, and tried to copy stuff to a different usb flash drive and it failed in exactly the same way every time. So now I now it's bad hardware. If I connect a usb 1.1 hub to force 1.1 speeds, it works fine, although very slow.

    If it worked okay in another os I would know it's a bad driver in windows 10.

    My first guess on your problem with the transfers speeding up and slowing down is maybe the write cache is filling up.
     
  8. eemuler

    eemuler MDL Senior Member

    Jul 31, 2015
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    The 100% disk usage is Windows Explorer. I'll try some Explorer tweaks like turning off search, prefetch, etc.
     
  9. Enthousiast

    Enthousiast MDL Tester

    Oct 30, 2009
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  10. eemuler

    eemuler MDL Senior Member

    Jul 31, 2015
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    It is like Explorer suddenly realises "Hey look , here are some new files. Let me index them, analyse and categorize them, scan them, create thumbnails for them etc. "
     
  11. MELERIX

    MELERIX MDL Addicted

    Nov 7, 2011
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    or maybe is related with thermal throttling in the SSD or another device.
     
  12. eemuler

    eemuler MDL Senior Member

    Jul 31, 2015
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    #12 eemuler, Sep 23, 2019
    Last edited: Sep 23, 2019
    (OP)
    CPU GPU SSD temperatures are fine - haven't checked the PCH.

    EDIT - PCH around 50 C.
     
  13. kaljukass

    kaljukass MDL Expert

    Nov 26, 2012
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    Everything is absolutely as it should, and if you don't know why it is so, it's time to learn why system works so if coping files.
    There is absolutely nothing wrong (or incorrect) with your system. Everything works absolutely right.
     
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  14. Flipp3r

    Flipp3r MDL Expert

    Feb 11, 2009
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    It's probably just Windows. I use Teracopy which is way better. Files get queued as well...
     
  15. eemuler

    eemuler MDL Senior Member

    Jul 31, 2015
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    That was the first thing I tried. Same issue.
     
  16. pf100

    pf100 MDL Expert

    Oct 22, 2010
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    I remember when Windows 10 was first introduced. File transfer speeds were horrible. They fixed it eventually, but is it still fixed? I don't know.
     
  17. eemuler

    eemuler MDL Senior Member

    Jul 31, 2015
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    Please be so kind as to explain to me why I should be satisfied with transfer speeds that are 10% of what they should be? Note: the files being copied are between 600 MB and 2 GB each.
    (I turned off 'show thumbnails instead of icons - no change).

    03.png 04.png
     
  18. endbase

    endbase MDL Guru

    Aug 12, 2012
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    If you are so worried about the speed you have to take in mind that you have a source disk and a target disk replace both with faster disks
     
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  19. eemuler

    eemuler MDL Senior Member

    Jul 31, 2015
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    The current source disk should give 90 to 120 MB/s sustained. I'm getting slowdowns to 10 MB/s. I've tried with the M2 SSD as the source disk - as reported earlier. M2 SSD to SATA SSD: ~500 MB/s and ~10MB/s
    Also, why the 100% disk usage? What is Explorer doing?

    06.png 07.png
     
  20. endbase

    endbase MDL Guru

    Aug 12, 2012
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    Maybe indexing or other stuff Why not do a clean install and test then ? it's a process of finding the cause it mostly takes time to figure things out in the mean time check the processes when disk is 100 % used
     
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