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omniaton

Download speed saturates speed but slows down soon after

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I'm on a Google Compute Engine VM so speeds to and from Google Drive should be pretty fast. I tested an upload with Google Filestream and was able to get speeds of 1.4gbps and an rclone upload hit 400mbps. I'm trying to move some data from the CloudDrive to rclone but am having trouble maintaining a high download speed. When I first start the transfer, I can get upwards of 700mbps but it soon crawls down from anywhere from 150 to 200mbps.

 

I tried downloading a file from the CloudDrive using Windows explorer to see more specific file speeds. It would initially start out really fast at 400 to 500mbps but drop down to around 5, drop to 0, and back up to 10 to 20 with the speeds fluctuating somewhere between there but never back to the initial fast speed. I assumed this might have an issue to do with the prefetch settings so I tried experimenting with them but nothing changed the speeds.

 

The drive was created with 20MB chunks, I tested 5 to 10 upload threads, minimum download sizes of 20MB to 100MB, prefetch trigger 5 to 20MB, forwards of 100 to 800MB, and a window of 30 seconds. I even disabled prefetching all together and experienced the same speeds. Something I also noticed was the threads used would fluctuate between 0 to 4 threads even though the maximum would be something like 10.

 

I'm pulling my head over here and would really appreciate any help. Thanks :)

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This is because it will initially prefetch multiple chunks with multiple threads. After the prefetch is retrieved, it will only download as required to keep the same prefetched amount.

 

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