I experienced some unexpected behavior trying to install a large program (60GB) on to my primary SSD at the same time as I was transferring a large file (2TB) between two HDDs: the installer slowed down to a crawl.

Additional Observations:

  • As soon as the file transfer finished, the installer resumed at normal speed. The two situations appear to be related
  • The source and destination of the installer are the same, that is to say that the installer was located on the SSD and was installing to the SSD. The source or destination disks of each file operation are different from one another.
  • The large file transfer between HDDs was completed at a constant 195MB/s. This is unusual: in the past, transferring large files like this on Windows would start at 195MB/s then slow down considerably to about 80-90MB/s
  • In Task Manager, I examined drive activity: the HDDs had a lot of activity but the SSD had no activity.
  • I didn't monitor RAM usage closely, but I did note that there was no unusually large usage reported.

System specs:

  • Windows 10 Pro 64-bit v1909
  • 32GB DDR4 Ram
  • Motherboard is GIGABYTE Z270X-UD5
  • Primary drive is a M.2 SATA SSD in M.2 slot (M2M_32G)
  • Two other HDD attached to the computer on SATA ports


What could cause this? And how can I remove or alleviate that bottleneck? My gut instinct is to suspect some hidden buffering system going on behind the scenes that is bottle necking this transfer. Especially if Windows is buffering to the SSD behind the scenes? If that's the case, is there a way to instruct Windows not to do this? This behavior also seems to be relatively recent.

  • My guess would be some bug/regression of the new Win10. Are you using the builtin AHCI driver btw? Or the Intel RST? – Tom Yan Nov 25 '19 at 18:43

What's the common factor for all three drives? Well, the SATA controller.

You could check your motherboard to see if it has multiple SATA controllers, and if so, move the SSD to the unused controller. If not, you could acquire a SATA controller card and move the HDDs to it.

Since you did not provide the make and model of the motherboard, there's not much more to suggest.

  • Thanks for the tip; I've added a bit more hardware detail. I will have to wait to get home to confirm which SATA ports each HDD is connected to. Could the issue be related to page 32 of the manual? download.gigabyte.com/FileList/Manual/… I'm pretty sure I double checked this before installing all the drives. – SkyNT Nov 25 '19 at 18:29
  • 195MB/s. I'd suppose even with a SATA 3.0Gb/s controller there's still more or less 50MB/s of bandwidth available. So 60GB should take around half an hour to go. Not sure if the OP would consider that a "crawl", but it's a DDR4 machine, so it's pretty much for sure a 6.0Gb/s controller. I doubt that 15min for 60GB would be considered a crawl. – Tom Yan Nov 25 '19 at 18:30
  • @SkyNT it shouldn't matter. quite obviously it's just a matter of mapping/wiring of the sata ports (like, if you connect a drive to an unavailable port, it simply wouldn't be detected at all). – Tom Yan Nov 25 '19 at 18:34
  • The file transfer between HDD took 2 hours. During that time the installer progressed maybe 1-2%. Once the file transfer was complete, the installation was able to complete thereafter in a matter of minutes. I might add that some of the applications installed on the main drive were a bit slow to launch as well. – SkyNT Nov 25 '19 at 18:36
  • While I don't think the SATA controller is supposed to pose such intolerable bottleneck, (yet) another alternative is to get some HDD docking / enclosure and (ab)use your USB 3.1 ports, for the record. – Tom Yan Nov 25 '19 at 18:50

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