USB Drive read/write 100%... very slow write

  1. Posts : 226
    Windows 10 (Home Ed.)

    USB Drive read/write 100%... very slow write

    I have a 6TB (mains-powered) external Seagate USB3 drive (used only for data backup) which might be failing? Or could there be another reason for the problem? Another, identical Seagate drive seems to perform OK (though I haven't done extensive side-by-side testing).

    When I start copying to the drive, it starts very fast, but after a minute or less slows to a crawl (500kb/s or less). In Task Manager/Performance, the disc shows 100% read/write, even after any copying has been cancelled. The drive then will prevent (or at least massively delay) Windows from shutting down 'Safely Remove drive' in the system tray doesn't respond.

    Checkdisk reports no errors.

    The issue, as far as I can tell, seems to be with writes to the drive: reads look fairly normal. The drive seems to perform better if, rather than copy a main folder with many subfolders (say, 20GB) at one go, I copy each subfolder (maybe 500MBs each) one by one. Doesn't seem to matter whether I am copying small or large files (or a mix). Also seems to perform better for longer in Windows 7, but it fairly soon slows to a crawl there too.

    The drive is set in Device Manager for 'better performance' (not quick removal) with write caching enabled - Windows write cache buffer on (off makes no difference).

    The drive is almost full - about 60GBs free out of 4TB, but would that matter??

    Thanks for any ideas on this. (Windows 10/20H2)

    USB Drive read/write 100%... very slow write-grab_043.jpg
    Last edited by martinlest; 08 May 2021 at 07:22.
      My Computers

  2. Posts : 1,564
    11, 10, 8.1 and 7 all Professional versions, and Linux Mint

    I do not understand the logic of trying to write to a drive that is 6TB and only has
    The drive is almost full - about 60GBs free out of 4TB, but would that matter??
    I am sure you know that the drive 6000 GB
    minimum effective space is 600GB

    SSD drives
    An SSD has an extra layer tied into free space and speed. When an SSD has empty blocks, the computer writes quickly to those blocks. If your SSD is nearly full to capacity, the program must find partially empty blocks, which takes longer.

    That all said is it
    I have a 6TB (mains-powered) external Seagate USB3 drive
    The drive is almost full - about 60GBs free out of 4TB, but would that matter??
    and sorry I did not spot the would it matter - before - the answer is Yes
    Last edited by Macboatmaster; 08 May 2021 at 14:00.
      My Computer

  3. Posts : 4,080
    Windows 7 HP 64 - Windows 10 Pro - Lubuntu

    Run a benchmark test
    Suggest to use Crystal Disk Mark . It is a portable, don't need to install. Extract and run.
    Post a image of the results
      My Computers

  4. Posts : 226
    Windows 10 (Home Ed.)
    Thread Starter

    Well, if the fact that there is little space left is the key factor, it is odd that I don't have the same issue with the identical drive I mentioned, which has the same amount of free space (more or less). In addition, the copying starts off very quickly and then suddenly slows down: seems unlikely it suddenly hits a 'critical' free space level. The free space I mention takes into account all the space needed by the drive itself of course - I expect to get about 5500MBs on a 6GB drive, maybe a bit less.

    The other thing that makes me wonder whether the problem is with the disc itself is that the problem is sometimes not apparent at all, especially (as I said) if the size of the folder being copied is relatively small. Yesterday, instead of copying one folder (containing 30 subfolders) of 30GBs, I broke the operation into smaller bits, as it were, and dragged over each individual subfolder to the drive in question: that's 30 folders of about 1GB each. The speed with which each one copied over was amazing, just a few seconds for each one - the speed showed about 200MB/s, which was about right by the clock.

    It seems that the sudden, very drastic slowing occurs after a certain amount of data is copied in one go. If you do it in smaller pieces, the files copy over before the 'buffer limit' (if that is what it is) is reached.

    Not sure if that makes any sense technically, but it is certainly what happens in practice - I copied all my files in record time by doing it is increments like this, just a couple of minutes, if that, (as opposed to the "120 days" estimated yesterday, at 150kb/s, or whatever). Also, the read-write % stays reasonably low and goes back to 0% when the copy is finished, rather than sticking at 100% until I reboot - even when no files are being copied.

    (I have also freed up a bit of space.. there's about 200MBs free on the drive at the moment: I use up a lot of storage space with what I do (satellite earth terrain images) - I have at least 15 drives ranging from 2 to 8TBs: I try to maximise the use of each one as far as possible for $$$ reasons!).

    I will try a benchmark at some stage soon too, but it'd be good to know why I can copy up to around 5-6GBs at a time (it seems) with no issue: if I copy more than that in one operation, the drive seems to hit a wall and doesn't free itself until I reboot. It's actually not the first drive I have had which shows exactly this odd (?) behaviour.

      My Computers

  5. Posts : 2,315
    Windows 10

    Nothing is wrong as such, the same thing happens when using File Explorer to copy files to a USB thumb/flash drive.The difference is the HDD has a buffer(cache) which accounts for the drive working after cancelling.

    It is particularly noticeable with large numbers of small files.

    As a simple experiment just ZIP your small files so you are just copying 1 large file, then you will find speeds are much better.

    I am no expert but the fluctuations seem to be something to do with a combination of the way the USB interface works and how the disc filing system works.
      My Computer

  6. Posts : 4,080
    Windows 7 HP 64 - Windows 10 Pro - Lubuntu

    The first M Bytes of a file are transferred to a buffer (RAM) and then from the buffer to the disk. That is why you see very fast transfers and then it slow down.
    Transferring a big file is completely different of transferring many files in sub folders.
    Did you run benchmark test?
      My Computers

  7. Posts : 2,766
    Windows 10 Home x64

    Make sure Write Caching is enabled. I think Windows standard policy is set for Quick Removal instead of speed. Double click on drive -> Propierties -> hardware -> properties -> change settings -> policies (or directives) (taken from Spanish).
      My Computer

  8. Posts : 1,564
    11, 10, 8.1 and 7 all Professional versions, and Linux Mint

    From the opening post
    The drive is set in Device Manager for 'better performance' (not quick removal) with write caching enabled -
      My Computer


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