Unless I've taken a wrong turn following the many abstraction layers, this file copy seems to involve connecting to a remote server and exchanging the file contents over a base64 stream (?) using nothing but a standard OutputStream to write the contents.
This means that whatever performance improvements Microsoft may have stuffed into their native network filesystem copy operations doesn't seem to get triggered. The impact will probably differ depending on if you're copying Windows-to-Windows or SAMBA-to-Windows or Windows-to-SAMBA.
However, the other measurements do show some rather weird slowdowns for basic filesystem operations over SFTP or WSL2. I think there's more at play there, as I've never seen sftp not reach at least a gigabit given enough time for the window sizes to grow. I think the NAS itself may not be very powerful/powerful enough to support many operations per second, limiting the output for other copy tools.
As an alternative, Windows contains an NFS client that can be tuned to be quite fast, which should have minimal performance overhead on Linux if kernel-NFS is available.
> connecting to a remote server and exchanging the file contents over a base64 stream (?)
I think that's not the right code because it's in "PerformCopyFileFromRemoteSession" and that sounds like it's for Copy-Item -ToSession ... -FromSession ... which are for New-PSSessions (PowerShell remoting/WinRM). Those are already Powershell-serialized-in-XML-in-WinRM-XML (I think) and copying file data plausibly goes into Base64 to go inside that.
That can't be what happens if you do Copy-Item -Destination \\server\share\
>PowerShell guru, but if you can write a (C#?) cmdlet
Yea, I have a workload that has to delete millions of directories/small files on occasion and we wrote a cmdlet to spawn a huge amount of threads to perform the delete to keep the IOPS saturated and it performs much better than explorer or other deletion methods.
Then, when the copying happens, this seems to be the code that actually copies the file, at least when copying from remote to local, using the default file system provider: https://github.com/PowerShell/PowerShell/blob/master/src/Sys...
Unless I've taken a wrong turn following the many abstraction layers, this file copy seems to involve connecting to a remote server and exchanging the file contents over a base64 stream (?) using nothing but a standard OutputStream to write the contents.
This means that whatever performance improvements Microsoft may have stuffed into their native network filesystem copy operations doesn't seem to get triggered. The impact will probably differ depending on if you're copying Windows-to-Windows or SAMBA-to-Windows or Windows-to-SAMBA.
I'm no PowerShell guru, but if you can write a (C#?) cmdlet to invoke https://learn.microsoft.com/en-us/windows/win32/api/shellapi... with a properly prepared https://learn.microsoft.com/en-us/windows/win32/api/shellapi... rather than use the native Copy-Item, I expect you'd get the exact same performance you'd get on Windows Explorer.
However, the other measurements do show some rather weird slowdowns for basic filesystem operations over SFTP or WSL2. I think there's more at play there, as I've never seen sftp not reach at least a gigabit given enough time for the window sizes to grow. I think the NAS itself may not be very powerful/powerful enough to support many operations per second, limiting the output for other copy tools.
As an alternative, Windows contains an NFS client that can be tuned to be quite fast, which should have minimal performance overhead on Linux if kernel-NFS is available.