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) so I'm protected against enclosure related issues (controller failure, power loss, cable disconnected etc.).
The enclosure being the problem was a bit of a strange end to that 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.