Horrible rsync performance on wd cloud vs My book live

Hey, folks – I just had an idea.

Might be real, might be tilting at windmills.

First, go check this thread:

http://community.wd.com/t5/WD-My-Cloud/HOW-TO-Troubleshoot-NAS-Performance-concerns/m-p/618695#U618695

I just updated that with a little information about IEEE 802.3x “Flow Control” which, not only does this NAS fully support (and is enabled by default) but appears to be actively functioning in my network.

Flow control has to be supported at BOTH ends of ALL links in order to be of full benefit.   The NAS, the Switch, and your PC(s) must support it to get the best results.

I just checked my switch statistics for Flow Control Pauses, and see the numbers increasing during large file transfers.  This is a GOOD THING.   Flow Control prevents a device from over-running the switches’ buffers by telling the sender to “Back Off” for a fraction of a second (VERY small fractions – HALF-MICROSECONDS at a time.)

This helps prevent TCP/IP retransmits, which cause significant slowdowns in otherwise fast networks.

My switches have 128Kbyte packet buffers.   So if the switch is sending Pause frames, that means the Cloud is sending data even faster than my switch can accept them.  

So if you’re using a switch that has tiny packet buffers (and MANY of them do) that can be a cause of slow performance.  The post I linked to above will tell you how to find out if that’s the case.

I don’t have any such switches to test on, so I can’t see what real benefit is coming from that.