OpenZFS on OS X

Hello developers,
I have a problem with the two or three latest versions for quite a while now (on a 2012 Macbook Retina with regularly updated OS X, currently 10.11.5):

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sudo zpool export <poolname>

hangs after successfully unmounting all filesystems -- every time. I cannot even kill the process, just close the terminal window (with a warning, because of a running process), but the process itself then is still hanging in the background: When I try to e.g. mount the filesystems again, this attempt fails too. The only thing that helps in my experience is rebooting the Macbook, which is quite annoying, because I reboot very rarely and my mindset is like "if I connect this external drive now, I cannot detach it until the next reboot! Hm, I better not this time." which kinda thwarts the whole idea of an external drive...
I had hoped for a fix with new versions, but it does not seem to be a common problem.

I'd love to give you more technical details, like reports/logs, but I don't remember how to enable verbose logging, where to find the logs etc.

Help would be highly appreciated,
rattlehead

Hi,

Sounds like something rather unique is happening to you. https://openzfsonosx.org/wiki/Getting_involved contains some instructions on how to gather a spindump, which you should do when you have a stuck export. Please join the IRC channel and bring your spindump for further support.

- Brendon

Brendon wrote:Please join the IRC channel and bring your spindump for further support.

Will do, thanx for the quick reply.

@rattlehead

We have looked at the dump you provided, and we can see where it is stopped. It is not clear _why_ its stopped at all.

Can you please describe your setup a bit (hardware, dataset layout etc etc) and also what is the system doing when you export?

Cheers
Brendon

Ok, here we go:
I) System setup
- Macbook Pro retina 2012 16GB RAM
- Usually connected is a Pegasus R8 (via Thunderbolt) with native RAID6 and HFS+, usually having constant but low activity
- Then from time to time I connect (via Thunderbolt) a Pegasus R6 with 6 x 8TB and a ZPOOL configuration like this:

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Fri May 22 11:40:28 CEST 2015
  pool: zfsraid
 state: ONLINE
  scan: resilvered 116K in 0h0m with 0 errors on Fri May 22 11:40:20 2015
config:

    NAME        STATE     READ WRITE CKSUM
    zfsraid     ONLINE       0     0     0   
      raidz2-0  ONLINE       0     0     0   
        disk9   ONLINE       0     0     0   
        disk2   ONLINE       0     0     0   
        disk7   ONLINE       0     0     0   
        disk6   ONLINE       0     0     0   
        disk10  ONLINE       0     0     0   
        disk8   ONLINE       0     0     0   

errors: No known data errors

- no duplication, atime switched off, 4k blocksize set, no compression, UTF-8, formD as character normalization
- I have two filesystems
1. zfsraid configured as specified above
2. zfsraid/logs with pretty much the same configuration, only difference is compression being switched on
- Usually, there is one other user logged in to the same machine locally (with GUI session) but if I remember correctly, the problem persisted even before I used to have that.

II) When I try to export the pool after having used the volume for a bit (played videos from there, moved files/folders around, etc.), then it could so far always unmount /Volumes/zfsraid/logs, but sometimes fails to unmount /Volumes/zfsraid, even if lsof does not show any processes accessing the volume (but I experienced that with other non-ZFS volumes, too. So I don't think this is an issue that you can fix).
Most of the times, the unmounting of /Volumes/zfsraid also succeeds, but the process does not return to the console, and I can wait for the "export successful" message literally forever (I have waited a couple of days one time, until I disconnected and turned the case off the hard way). In those cases, I usually close all my programs and processes and try a clean shutdown/reboot, which most often succeeds, sometimes in the past not, in which case I turned off the computer via the Power button. After the reboot (and given a few moments), the volumes are mounted without importing them (so they still are imported from the last session(?)). Often with much activity on the drives of the zpool. I usually do the export, after the drive activity comes to a hold (not having created any activity on the drives myself since the reboot). These times, the exports are usually successful.

Cheers
rattlehead

Are you able to compile our code?

Cheers
Brendon

I don't know how to do that.

What should I do now?

Same problem here. What worked for me was to permanently shut off
Spotlight, from the command line, this way: (El Capitan)

sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist

After doing that, sudo zpool export works every time. Slight delay, maybe 5 seconds, and then its done.

Note that just dragging the icon into System Preferences, Spotlight, Privacy, did NOT work.

Only shutting off Spotlight worked for me.

@jimserac

Thanks for the suggestion. However I would just like to note that this should not be required, and in fact I don't do it (I have no trouble with export).

We have some supporting log data from this user and we know where it hangs, just dont quite understand why. There is a good chance that its not a software issue, or if it is then a fairly unique one. Lundman is preparing and instrumented build to help this guy diagnose the problem as far as I know.

- Brendon