File Transfer Speed Issues on Windows 8.1

[canadaboy25]

Hey guys,

I'm having some problems with the file transfer speeds on my Windows 8.1 PC. The problem is whenever I copy a file, it starts off copying really quickly, but shortly after the file transfer begins, the speed drops right off.

This happens when copying between hard drives or to a USB.

I have attached a picture of a file transfer.

[joshnz]

Re: File Transfer Speed Issues on Windows 8.1

These drives are disk type?

[canadaboy25]

Re: File Transfer Speed Issues on Windows 8.1

These drives are disk type?

The attached picture was a transfer from an SSD to a HDD drive. Both SATA.

[Per Hansson]

Re: File Transfer Speed Issues on Windows 8.1

The speed is normal, first Windows caches some in RAM, and then you have insane speeds.
Then you see it has settled down at 67MB/sec which is normal sustained write speed for the kind of drives you describe.

[RJARRRPCGP]

Re: File Transfer Speed Issues on Windows 8.1

67MB/sec

Typical for a 2006 and 2007 HDD. (Especially <400 GB)

[Per Hansson]

Re: File Transfer Speed Issues on Windows 8.1

It was more the fact he said USB

[canadaboy25]

Re: File Transfer Speed Issues on Windows 8.1

The hard drive and SSD are only slightly over a year old. The hard drive is actually two 1TB hard drives in a raid array. The image I attached was of a copy from my SSD to the HDD array.

This also occurs when copying from the SSD to a USB flash drive

[mariushm]

Re: File Transfer Speed Issues on Windows 8.1

The USB drivers have a write cache, meant to make applications seem faster by caching small writes to memory before writing to a usb mass storage device.

As a fictional example, an application like MS Word would save to disk by creating a temporary file, writing the stuff in it, then deleting the original file and renaming the temporary file with the original file name. As USB devices are much slower to respond (latency) and their speed is usually very small when it comes to writing small chunks of data (in the range of 500 KB/s - 1 MB/s), it would take a bit of time for the document to be saved, maybe a couple of seconds or even more, so it would seem to you that the application is slow.
So, the operating system and the usb drivers have a system, a cache, in which as long as the usb driver knows the mass storage device is plugged in, the usb driver caches those writes and tells the operating system (and applications) that they were performed while in reality they still happen slowly in the background.
So Word almost instantly sees the document was saved to disk while in reality it's somewhere in usb driver's ram still being written to the USB stick.

Same with copying small files to usb stick - with lots of small files, this really helps with transfer speeds, usb sticks like large transfers.

In addition, Windows also has a system in which it caches files to portions of RAM that aren't used by programs. For example, if you start to watch a movie, Windows may start to copy the movie in advance to memory and keep it there, serving the movie to the player application from ram instead of the hard disk.

If you happen to copy a file to usb and that file or a portion of it was cached by Windows to memory, you'd see that huge initial speed (because as far as it's concerned, windows told the usb drivers to copy that portion of memory to usb storage and from that point it considers the data written to disk) and the usb driver writes stuff to disk in background.

At some point the usb driver's cache fills up with write commands and stops taking requests from the operating system until it empties a bit, and that's when you actually start to see the real speed of your usb device... until the copying process is complete, the driver will always have its cache full with commands from the operating system so it's basically limited by the usb storage device (stick, drive etc)

[canadaboy25]

Re: File Transfer Speed Issues on Windows 8.1

The USB drivers have a write cache, meant to make applications seem faster by caching small writes to memory before writing to a usb mass storage device.

As a fictional example, an application like MS Word would save to disk by creating a temporary file, writing the stuff in it, then deleting the original file and renaming the temporary file with the original file name. As USB devices are much slower to respond (latency) and their speed is usually very small when it comes to writing small chunks of data (in the range of 500 KB/s - 1 MB/s), it would take a bit of time for the document to be saved, maybe a couple of seconds or even more, so it would seem to you that the application is slow.
So, the operating system and the usb drivers have a system, a cache, in which as long as the usb driver knows the mass storage device is plugged in, the usb driver caches those writes and tells the operating system (and applications) that they were performed while in reality they still happen slowly in the background.
So Word almost instantly sees the document was saved to disk while in reality it's somewhere in usb driver's ram still being written to the USB stick.

Same with copying small files to usb stick - with lots of small files, this really helps with transfer speeds, usb sticks like large transfers.

In addition, Windows also has a system in which it caches files to portions of RAM that aren't used by programs. For example, if you start to watch a movie, Windows may start to copy the movie in advance to memory and keep it there, serving the movie to the player application from ram instead of the hard disk.

If you happen to copy a file to usb and that file or a portion of it was cached by Windows to memory, you'd see that huge initial speed (because as far as it's concerned, windows told the usb drivers to copy that portion of memory to usb storage and from that point it considers the data written to disk) and the usb driver writes stuff to disk in background.

At some point the usb driver's cache fills up with write commands and stops taking requests from the operating system until it empties a bit, and that's when you actually start to see the real speed of your usb device... until the copying process is complete, the driver will always have its cache full with commands from the operating system so it's basically limited by the usb storage device (stick, drive etc)

Thank you very much for taking the time to explain it so clearly. I now understand what is happening.

I just wanted to make sure that there isn't some hidden performance issue that I'm having.