Hello,
I've provided a very basic drawing of a client's configuration below. Please excuse the crudity or possible inaccuracy of the drawing. Feel free to correct it if I'm completely off-base. Onto the problem/question...We're currently seeing some inconsistent transfer speeds in certain scenarios between these two hosts. All transfers were done with a 6GB ISO file. Here's the breakdown:
Virtual machine A transfer to virtual machine D runs at full 1Gbps speed (or 125MBps). (In this example we are logged in to Windows and simply copy the ISO via UNC from virtual machine A to D).
The same is true in reverse. D to A runs at the same speed.
If we login to vCenter and attempt to copy that same 6GB ISO from Datastore 1 to Datastore 2, then the transfer never hits full 1Gbps. In fact, it's pretty much exactly half. It will never go faster than about 500Mbps. The same is true in reverse here as well. Datastore 2 to Datastore 1 runs at the same speed.
Oddly enough, we're seeing the same "half speed" when the backup appliance (it's a Datto with SSD storage) tries to backup virtual machines that are sitting on Datastore 1 (haven't tested Datastore 2 virtual machine backups yet). The transfer speed will never go faster than 500Mbps.
What gives? My first thoughts are along the lines of a duplex setting but we've checked all devices involved and everything is running at 1Gbps. The other thing that steers me away from a duplex problem is the fact that when I transfer between virtual machines on the two separate hosts I can hit full 1Gbps speed no problem. I conjecture that the data is following a different path in these two different transfer scenarios but I don't quite understand how or why. I'm also wondering if something isn't configured correctly at the host or datastore level. Any thoughts?
