Robocopy multi-threaded copies

Question

_{Monday, December 18, 2017 8:59 AM}

Greetings,

I'm using Robocopy to copy my user files (%userProfile%) to an external USB 3.0 hard drive. Copying 350 GB used to take one hour, now it takes five or six hours. I would like to try Robocopy's multi-threaded option (/mt), but I can't find any documentation on it, other than what it says in the command line.

The default value for multi-threaded (/mt) is 8 threads. Where should I start? Task Manager says my laptop has two cores and four logical processors.

The range for multi-threaded is 1 to 128. Could anything bad happen if I try a value too high?

I realise that this is probably going to be trial-and-error to find out what works, but I'm wondering what factors should be considered. For example, I read somewhere that /mt doesn't work well with large files, so I'm going to try it first with small to medium sized files.

Thanks,
Shane.

Windows 10 Home 64-bit

All replies (3)

_{Tuesday, December 19, 2017 7:05 AM}

Hi Shane,

Thank you for your post.

Based on my check, the application can now run in multi-threaded mode using the /MT option. This defaults to 8 threads, but users can specify up to 128 if desired. Whether you should stick with the default 8 threads or up it to 16 or 32 depends on the capabilities of your CPU, but it’s worth a try. I'll use 32 threads in my example, as I found it to be a good starting point.

http://blog.fosketts.net/2010/03/25/robocopy-multi-threaded/

Note that the multi-threaded option is not compatible with the /IPG and /EFSRAW options.

How to: Robocopy with Multi-Threaded Copy (it is suit for Windows 10)

https://community.spiceworks.com/how_to/1350-windows-7-robocopy-with-multi-threaded-copy

Please Note: Since the website is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

Hope it will be helpful to you

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_{Tuesday, December 19, 2017 9:10 AM}

Thanks for the links. I've started to experiment.

Specifying multi-threaded copies (/mt) messes up the log file. For example, it forces no directory list (/ndl) and full paths (/fp). Also, entries are written to the log file asynchronously. For example, a line could be in the process of being written to the log file, when a new line starts being written to it, before the existing line is finished.

Thanks,
Shane.

Windows 10 Home 64-bit

_{Friday, February 9, 2018 7:40 AM}

Over the past several weeks I've been experimenting with multi-threaded copies. The fastest transfers for an external usb3 drive is 8 threads (the default), and 16 threads for a network drive.

As I said, the default for the /mt option is 8 threads. Does this mean if I completely omit the argument that it is still 8 threads? Or does Robocopy become single-threaded?

I close all other applications when running Robocopy. Does anyone think increasing the processor priority for the command line would help at all?

Thanks,
Shane.

Windows 10 Home 64-bit