W7 copy to external HDD

I'm copying something from my DVDs to HDD, external one. W7 is copying the file first on the laptop HDD and then on the external. On the fly. Laptop HDD LED is constantly on, writing and reading I guess al the time and external HDD Led is on every few secs. So the copy speed is 6Mb/sec. Why is that? Everything is OK with both HDD.

 

- DVD data rate limit? DVD-R - Wikipedia, the free encyclopedia

- File size. The bigger files you copy, like movies, the faster it gets copied.
If you copy thousands of tiny files, like the contents of a Windows install DVD (not as a whole ISO image) it will be slower.

- If you think the simultaneous read/write is the reason for the slow down, try copying some files directly to the laptop HDD (not to the USB) and see if it goes any faster.

 

I'm copying one file and it's an .iso file and to make it clear I'm not ripping the DVD, .iso is already on the DVD as an .iso file. So i't should be atmax speed, usually I get around 27MB/s.

If I copy directly to laptop HDD I get 10MB/s.

 

If the hard drive in your laptop and the DVD drive share the same controller, then you will notice a decrease in speed. This is because the controller has to balance the bandwidth between both devices and has to give ample time to each device in order to flush each device's cache before the next read cycle.

When you copied to the external, the controller in your laptop really only had to handle 1 device, the DVD drive. The USB controller connected to the external hard drive controller handled the transactions for the external hard drive. Hence, you saw a greater speed.

 

I think you misunderstood my post. When copying to external from DVD, first it's beeing copied to laptop HDD and then to external. That is 6MB/s. If I copy only to laptop HDD then I get 10MB/s.

 

Then what you are seeing is the effect of overhead. In the first scenario, you are looking at going through 3 different controllers, one of which is simultaneously reading/writing. The second case, you are only dealing with 1 controller.

 

I still don't understand why is the laptop HDD being used. I've never had that happening.