jawbroken wrote:The person who opened this issue, that you already commented on, seems to have eventually tracked it down to their enclosure. So I should probably also say that my ZFS drives are in a few of these Thunderbolt enclosures.
The enclosures I'm using are the four disk versions of yours; I should have said, I have two, with the disks split between them (I basically have three mirrored pairs, so I've split the disks between the two enclosures, with one bay free in each) so I should be protected against enclosure related issues (controller failure, power loss, loose cable etc.).
The enclosure being the problem was a bit of a strange end to that Github issue though, since they seemed to be getting different results with and without encryption; I can't think of any reason why that would make a difference if the enclosure were the problem, unless it was part of a new setup (copied their data across to a new encrypted dataset in the slower enclosure), i.e- their unencrypted test was a different enclosure, and they hadn't eliminated that difference already?
So while I did initially think the issues might be related I'm sceptical whether it's the same cause; they noticed no improvement when bypassing cache, whereas disabling ARC (primarycache=none, secondarycache=none) makes a huge and immediate difference whenever I test a version from 2.1.6 onwards, and others reporting the same problem have seen the same improvement.
And like I say, 2.1.0 works just fine, so the issue is definitely related to something that changed in ZFS.