A year ago I set up Ubuntu server with 3 ZFS pools on my server, normally I don’t make copies of very large files but today I was making a copy of a ~30GB directory and I saw in rsync that the transfer doesn’t exceed 3mb/s (cp is also very slow).
What is the best file system that “just works”? I’m thinking of migrating everything to ext4
EDIT: I really like the automatic pool recovery feature in ZFS, has saved me from 1 hard drive failure so far
You could try to redo the copy and monitor the system in htop, for example. Maybe there’s a memory or CPU bottleneck. Maybe one of your drives is failing, maybe you’ve got a directory with tons of very small files, which causes a lot of overhead.