OpenZFS ZFS-OSX: reduction of bugs(s) that affect some uses of home directories

[Graham Perrin]

Related: 

Desktop freezes while using zfs volume as home directory

<https://github.com/zfs-osx/zfs/issues/57> by Brendon Humphrey

OpenZFS ZFS-OSX (osx.zfs-20130930.dmg): testing

<https://groups.google.com/d/msg/maczfs-devel/o11uAjEcHlE/EJzgJVAQYlIJ>

OpenZFS ZFS-OSX (osx.zfs-signed-20131011.dmg): testing

<https://groups.google.com/d/msg/maczfs-devel/s2m474kt3Sk/cl-EpePRiYUJ> 

> … try to find the minimal amount of steps required to trigger this issue. 

Jorgen, please: are the symptoms in your case similar to those in Brendon's case? Can you add any additional description of the sequence of events and symptoms/deterioration? 

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For reduction purposes, you might try the following: 

01) OS X 10.8.4 or 10.8.5 in a virtual machine

    – there's not yet a kernel debug kit for 10.8.5, if that's relevant

02) in the virtual machine, use ZFS-OSX to create a pool

03) in the VM, make a subdirectory of a ZFS file system an AFP share point

    – not the root of a file system

04) in the VM, make a subdirectory of that share point an AFP home directory

05) use a physical machine as the client; log in to the AFP home directory. 

OS X Server <https://itunes.apple.com/gb/app/os-x-server/id537441259?mt=12> may streamline part of what's above. 

Whilst I have not taken that approach, my instinct is that – *if* there's a mass of home directory data and relatively heavy usage – server-side, you'll observe some thought provoking behaviours (or clear issues). 

AFP homes on ZFS (is it even possible?) may be not a realistic use case, but I reckon that somewhere amongst the behaviours: 

* you'll find a clue to the #1 cause of home directory issues where there's _not_ AFP.

Hope that helps. I understand that developers might require a more focused approach ;-)

Graham

[ilov...@icloud.com]

Yes, people do ZFS (and Ext4 and Btrfs) home directories via AFP with Netatalk all the time. I haven't tried it with ZEVO or MacZFS though.

Theoretically, although probably not the best idea for testing this particular issue, you don't need a VM or a second machine to use AFP. You can just do a port forward with socat (grab it from homebrew or macports) or ssh. For example:

sudo socat -d -d TCP4-LISTEN:5248,bind=127.0.0.1,reuseaddr,fork,su=nobody TCP4:127.0.0.1:548,bind=127.0.0.1

Then you can mount your current machine's afp shares. command + k in Finder, and connect to afp://127.0.0.1:5248 or just 127.0.0.1:5248.

[George]

Would it help anyone if I were able to contribute private remote access to a VM installation that could be used in troubleshooting of these issues?

[Graham Perrin]

On Saturday, 12 October 2013 11:49:38 UTC+1, ilov...@icloud.com wrote:

… Theoretically, although probably not the best idea for testing this particular issue, you don't need a VM or a second machine to use AFP.

My nudge towards separate machines arises from observation of the range/overlap of symptoms when a single machine was used. 

When top(1) ceases to work as expected (see issue 57) – when other things cease to work as expected – then for example we can not expect meaningful output from things such as sysdiagnose(1). In the ZEVO support forum –

some ZFS-related improvements to sysdiagnose

<http://zevo.getgreenbytes.com/forum/viewtopic.php?t=1647>

– in particular: 

>> sysdiagnose seems unable to move on in troublesome environments

My sense of Mavericks, from limited testing: sysdiagnose *is* improved in that area – but not enough to allow for the range of troubles that I observed in my home directory-oriented tests of ZFS-OSX. 

AFP service in a separate machine, ideally a virtually machine, *might* increase the likelihood of gathering relevant information before the machine is brought to its knees. 

If you're unlucky, the separation will simply not trigger the bugs :-(

----

Without attempting the broad-range gathering that's normally performed by sysdiagnose: I see Brendon taking more focused approaches :-) 

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… Then you can mount your current machine's afp shares.… 

If mount of the AFP home directory is automated, as part of the operating system's routine (not scripted/automated in any other way), then you'll probably find part(s) of the file system used in a way … a way that does not occur when using AFP for the same data *without* the home directory login routine of the OS. 

I must say that it's years since I paid any special attention to how HFS Plus is used in an AFP home directory environment. (For most purposes, Mac OS X Server was/is something that just worked.) So if anyone does choose to take this 'separate machine + AFP' approach to troubleshooting the ZFS home directory issues: 

* don't waste too much time on it

… but if you do take the approach, *maybe* pay a little attention to modes and ACLs during or shortly after the home directory login routine. I have a *very vague* recollection (from long before any interest in ZFS) of being taken by surprise by some file system activities.