I have two Windows 10 computers directly networked together, but when I copy a single, huge file (20GB) between them, I get performance that looks like this:
For some reason, after a certain period of time, the copy speed falls off a cliff and then ramps back up. I can't really tell what's happening. When I copy the file over a gigabit or 2.5 gigabit connection, I never observe this behavior. But when the connection is 750 MB/sec (first example) or 2 GB/sec (second example), I see this.
I guess it could be the SSD write caches filling up, but I thought that would look different, something like this for example:
Given that's not what I'm seeing, and considering I see the same behavior no matter which pair of SSDs I'm copying between (Samsung 980 Pro, Samsung 970 Evo +, TeamGroup A440 Pro, Samsung MZVLQ512HBLU), I suspect it's something else. So maybe it's a Windows problem, or maybe it's related to how my network adapters are configured. I'm not sure.
I've seen this with two networking setups; two Intel XL710-XDA2 cards connected with a QSFP+ cable, and an OWC 10G Ethernet card connected to a Mellanox Connect-X2 card using an SFP+ to ethernet adapter. Both setups gave me file copies with V shaped dips like that.
Maybe there is a similarity in how the adapters are configured by default. Maybe there's a certain setting that could cause this? Any of these, maybe?
One computer has a Ryzen 7950X CPU and the other has an Intel i7-9750H CPU, in case that's relevant. Both are running Windows 10 21H2 (build 19044).
Any ideas what causes this behavior, and what I should try changing to fix it?
EDIT:
I tested copying the same 20GB file directly between the SSDs on the same system (so not over the network). They copied at a constant 1.8 to 2.2 GB/sec (depending on which pair of SSDs I was testing) the entire time, over the entire transfer. So I'm pretty sure this is networking related, and not SSD cache related.
For some reason, after a certain period of time, the copy speed falls off a cliff and then ramps back up. I can't really tell what's happening. When I copy the file over a gigabit or 2.5 gigabit connection, I never observe this behavior. But when the connection is 750 MB/sec (first example) or 2 GB/sec (second example), I see this.
I guess it could be the SSD write caches filling up, but I thought that would look different, something like this for example:
Given that's not what I'm seeing, and considering I see the same behavior no matter which pair of SSDs I'm copying between (Samsung 980 Pro, Samsung 970 Evo +, TeamGroup A440 Pro, Samsung MZVLQ512HBLU), I suspect it's something else. So maybe it's a Windows problem, or maybe it's related to how my network adapters are configured. I'm not sure.
I've seen this with two networking setups; two Intel XL710-XDA2 cards connected with a QSFP+ cable, and an OWC 10G Ethernet card connected to a Mellanox Connect-X2 card using an SFP+ to ethernet adapter. Both setups gave me file copies with V shaped dips like that.
Maybe there is a similarity in how the adapters are configured by default. Maybe there's a certain setting that could cause this? Any of these, maybe?
One computer has a Ryzen 7950X CPU and the other has an Intel i7-9750H CPU, in case that's relevant. Both are running Windows 10 21H2 (build 19044).
Any ideas what causes this behavior, and what I should try changing to fix it?
EDIT:
I tested copying the same 20GB file directly between the SSDs on the same system (so not over the network). They copied at a constant 1.8 to 2.2 GB/sec (depending on which pair of SSDs I was testing) the entire time, over the entire transfer. So I'm pretty sure this is networking related, and not SSD cache related.
Last edited: