This isn't my first rodeo, and my Mac is in fact NOT my machine that only has USB ports for external disks (it still has FireWire 800, plus a Thunderbolt1 port - but that one is occupied). Backing up a pool of a few 100 Gb over gigabit ethernet is just not an option, so USB *has* to work for me.
nodarkthings wrote:Yes, it's an old USB2 dock (and I don't have a clue of what UAS(P) is
) so I guess your hypothesis about 2.2.x bandwidth could matter (but why is it working in 10.11 and 10.14, then?
)
You misread me, I was thinking that USB3 might be the problem because that's my experience. UAS(P) is a newer "super protocol" that allows better throughput. It can be instable in older Linux kernel versions combined with certain chipsets in the external device but I never heard of problems with it in OS X 10.9 .
However, I would not be surprised if your use of a dock (powered hub?) are increasing your chances for the kind of problems on which the old "don't use ZFS over USB" is based.
I have a dual-device mirrored pool, two M.2 SSDs in USB3 enclosures. I connect those via a small non-powered USB3 dock to one of the ports in my Thunderbolt dock (which gives me my USB3 ports!). I have been using ZFS 2.1.0.4 (latest commit from the 2.1 branch, self-built) until now and have resilvered the mirror device in that pool multiple times now. I think there's about 20Gb of data on the pool without any issues, and resilvering is something that reaches much higher throughput rates than you get from copying a folder (unless it has huge files in it).
Evidently you can mix and match ZFS 2.1 with 2.2 on different machines. I prefer to avoid it because I don't want to see continuous messages about pools that can be upgraded, or run the risk that a pool I create on 1 system won't import on the other. But I just saw that I might get that even with 2.1.6 because someone backported 2.2 features that aren't available in ZoL 2.1.x (like Blake3 checksums).