dd if=/dev/null of=<mount-point>/test.file bs=1G count=10 status=progress

/dev/null tests from dd are not an accurate indicator of performance unless you only have one disk in your pool. fio is a much more accurate tool for zfs pool testing.

Eh… Maybe for learning.

Although they technically support vt-d, performance on 13-year-old machines will be pretty abysmal by today’s standards.

Lots of variables here, we would need to pare them down:

• architecture of zfs pool? This can be done well or very poorly, zfs gives you a lot of rope, if you know what I mean.
• memory?
• have you tuned samba ?
• are you trying to do anything fancy like jumbo frames ?
• what networking equipment lies between the two?
• do you have the correct and correctly configured 2.5gb driver for linux ? Intel 2.5 NICs had some issues for a while.
• what does the windows net hardware look like?

In troubleshooting transfer speeds , there are solo many variables, as you can see.

Start with the network and reduce variables until you have a likely source of the problem.

Love that for you.

However, that is not everyone’s experience and doesn’t really answer op’s question.