Copy-Item is 27% slower than File Explorer

Summary

1 2 3 4 5 File Explorer drag & drop ########## (112 MBps) Copy-Item ####### (82 MBps) Built in SFTP client ###### (70 MBps) Built in robocopy ## (25 MBps) WSL 2 rsync # (13 MBps) In table form:ToolSpeed (MBps)DifferenceDrag and drop~112—Copy-Item~82-27%sftp~70-37%robocopy~25 MBps-78%rsync (WSL 2)~13 MBps-88%I feel like I’m losing my mind.It all started innocently enough with a misconfigured NAS. I’ve been making some investments into the homelab recently, both for professional reasons and personal curiosity; by now I consider a couple of long CAT 7 cables and some unmanaged 1 Gbps Ethernet switches to be some of the best money I’ve spent this year. Every device in our home has a cozy data autobahn to rush down to talk to every other device in our home, and what’s more, I’ve actually seen rsync copy files from my NAS to my Debian daily driver at 100+ MBps quite regularly.But even after I un-mis-configured the NAS, I was surprised to find that rsync on Windows Subsystem for Linux pulled in data at a paltry 9 MBps, for an ideal use case (one large file). Removing the -z compression flag moved us up by 30-50%, which is commendable, but not the order of magnitude increase I was doubtfully hoping for.Was something wrong with the connection? Getting up from the strandmon would have required physical movement, so instead I just took that same exact file via the File Explorer network share, and just Ctrl-C Ctrl-V’d it onto my desktop - and I was immediately hitting 111-112 MBps again! There goes that theory. The calls are coming from inside the house.I don’t have much occasion to use these skills these days, but I actually became a somewhat proficient PowerShell user and Windows admin back in my first job. My curiosity was fully piqued by this point so I busted out Old Reliable - robocopy, rsync before rsync. It’s been built in since Windows 7 and handles an absurd number of weird edge cases due to its longevity, so you would expect it to be, well, fast, right. Like this is ...