Why do transfer speeds bottom out?

[JP]

I just built a new unraid server and everything appears to be working fine, but there is one issue I had with my previous 11 year old unraid server that has made its way to this new server.  That is, when transferring data across the LAN my Unraid server will accept data at very fast speeds (to me at least), around 140 - 300 MB/sec depending on the source.  However, almost always, at some point, if I'm transferring a significant amount of data, the transfer will bottom out and stall.  After 15 - 30 seconds maybe, it will pick things back up.  This is not due to waiting on a drive to spin up since I've also tested this from a cache drive to a single drive that is connected by USB.  They were both spun up.  

 

What is the culprit here?  I've done these transfers and watched my CPU and RAM.  Both are practically untouched with the CPU not even getting into double digits and the RAM having tons of space remaining.  What am I missing?  This screenshot is a good example.  It transferred at amazingly fast speeds and then bottomed out to 0 bytes / sec.

 

In case it helps, the new server I built has:

 

• CPU:  Intel i5 - 12400
• Motherboard - Asrock Steel Legend Z690
• RAM:  32 GB (dual channel) G.Skill

[itimpi]

The delays are probably occurring when flushing RAM buffers to physical disks.

 

you can never achieve anywhere near the native write speed of a drive as under Unraid a write operation always involves multiple I/O operations.    This is described 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.

[JP]

4 minutes ago, itimpi said:

The delays are probably occurring when flushing RAM buffers to physical disks.

 

you can never achieve anywhere near the native write speed of a drive as under Unraid a write operation always involves multiple I/O operations.    This is described 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.

 

Thanks.  So if the "flushing RAM" had more space, I would probably have more time and data that gets passed before it bottoms out...correct?  I have 32 GBs of RAM now.  I'm thinking if I double that, it might be money well spent.  

 

I do leverage a cache drive, but that is only for data that isn't terribly important for me.