My write speed fluctuate up and down

[skoub]

Hi everyone!

 

When i write to my shares, i do not get a smooth write speed. It always fluctuate up and down from 18mb/sec to 38-39mb/sec. I'm alone on my network, using an USB3 Gigabit Ethernet adapter. Is it possible to test write speed on my shares without using my laptop so i can remove my Ethernet adapter from the equation?

 

 

Here's my server:

 

tower-diagnostics-20190805-0200.zip

Edited August 5, 2019 by skoub
added diagnostic file

[skoub]

25 minutes ago, BRiT said:

Most troubleshooting helpers will need your full Diagnostics file to be posted.

done!

[Frank1940]

What exactly are you copying?  Large  files (>5GB) or thousands of small files (~5KB)?  When copying small files, the file creation overhead plus the lactancy introduced by the HD's read-write heads has a significant impact on write speeds.  

 

It always best to post up any new information (like your diagnostics file) in a new post rather than adding it to an old post by editing that post.   Editing an old post will not result in the folks following your thread receiving an email about the additional new material. 

Edited August 5, 2019 by Frank1940

[skoub]

@Frank1940, i'm copying large files >2GB. The spikes that I get is during the transfert of the same file.

 

And thank you for the tip about posting updates on a new post! It make sens!

 

 

[Frank1940]

OK, 2GB are not really large files...   But let's explain a bit about how Unraid copies files.  First thing that I noticed is that you are using a 500GB HD cache drive with a spindle speed of 5900rpm. That cache drive will probably not be near as fast compared to your data drives.

 

When you start a file transfer, Unraid will use any unused RAM to buffer the data being as it is received over the network.  This means that the data transfer to the server will be limited by the speed of the network.  Once that RAM buffer fills up, the data transfer rate will drop to the speed of the data writing speed of the cache drive.  Now, I am assuming that you have set up your shares to use that cache drive...

 

One more thing.  unless you change your cache drive to a fast SSD cache drive, your transfers will never equal the network speed once the RAM buffer fills up.  Thus, you will see a drop in the transfer speeds.  And that speed will functate up-and-down with the file creation overhead. 

[skoub]

My shares doesn't use the cache drive. But to push the test further, i tried to write directly to the cache drive.

 

This test is with a new share with the option "Use cache disc" to "Only". I obtain a stable 111mb/sec.

 

This test is with a new share with the option "Use cache disc" to "Yes". The transfert is not as smooth varying from 92mb to 111mb/sec