I just installed a 3 drive RAIDZ in my small home server to replace my old drives. But I don’t have enough SATA ports to also connect my old drives because the 4th SATA port is blocked when using a M.2 SSD, which I do as my boot drive. So I can’t transfer around 10 TB of files from my old drives to the ZFS pool. I have an external USB connector, but it’s really slow or I could boot from an USB stick, install ZFS and use all 4 SATA ports to transfer the files. I also have another PC to put the old drives in, but it would be quite a hassle.
Do you have any idea what would be the best solution to this?
I haven’t used raidz but a quick search tells me it supports single-drive expansion.
Maybe reconfigure your raidz as a 2-drive system, then copy over all your data into it, and expand it back into a 3-drive system after.