Hello,

 

I am transferring large media files from an Unassigned Device to the Array (a User Share) and things started out fine, ~180 MB/s, but have significantly dropped down to around 70 MB/s. Is there anything I can do to improve disk to disk transfer speeds? Any reason why this happens? I am using Dynamix File Manager to transfer the files. 

 

That seems a not unusual speed - I suspect initial boost was due to,RAM caching.    Do you have Turbo Write mode enabled (which is likely to even get 70 MB/s).   More information on Unraid array write modes can be found here in the online documentation accessible via the ‘Manual’ link at the bottom of the GUI or the DOCS link at the top of each forum page.

I did not, it was set to Auto:

 

Great call!!!! I read the documentation and gave it a shot. It's flying now:

 

I was concerned about the 68 MB/s because I saw writes going much faster on my parity drive during the initial parity build. The disk being written to is a Exos X20 which was advertised to go up to 285 MB/s. 

 

Thank you for the help! Should I set this back to auto once my initial data transfer is complete and I'm less concerned with write speed? Seems like the smart thing to do so every disk doesn't need to spin for a write. 

17 minutes ago, manofoz said:

I was concerned about the 68 MB/s because I saw writes going much faster on my parity drive during the initial parity build.

 

A parity check tends to be a special case as it is a serial write so basically no head movement most of the time.   Raw disk speeds quoted also tend to be hard to achieve except in special hardware+software test environments.

 

17 minutes ago, manofoz said:

Should I set this back to auto once my initial data transfer is complete and I'm less concerned with write speed? Seems like the smart thing to do so every disk doesn't need to spin for a write. 

Really up to you.   As you said it is a trade-off between write speed and power consumption required to keep all drives spinning.