Warren - Ep.273: OpenZFS on OS X

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Alan made several statements I’d like to push back on regarding OpenZFS on OS X.

First, installing from source is almost never necessary.  You want to be using the stable binary packages unless you’re helping with the actual development of O3X or are trying to provide stack traces and such for helping one of the developers.

Second, things are not exactly the same regarding actual use of ZFS on macOS as compared to using it on FreeBSD, Linux, Illumos, etc. due to the nature of the platform.  For instance, you almost always want to create a pool with two non-default options on macOS:

    -O casesensitivity=insensitive -O normalization=formD

These options change ZFS’s behavior to match that of the default HFS+ behavior, which apps on macOS may expect.  The latter is especially important to get right, since unlike many other ZFS options, you can’t change it after the filesystem is created.

Third, the cosmetic /dev/ada0blabla vs /dev/disk12 thing is just a minor detail when it comes to O3X, because it has a feature called InvariantDisks which creates a logical tree of /dev name aliases under /var/run/disk, mimicking the similar /dev/disk feature of Linux.

It’s very useful to use these features with zpool import -d because it makes your pool immune to silly storage bus renumbering problems, as may happen when you rearrange your Thunderbolt cabling to allow a new device to be added to the chain.

It’s been a while since I ran ZFS on FreeBSD, so I’m running on memory and web searches, but as far as I can tell, FreeBSD has only partial equivalencies.  For example, its /dev/gptid feature appears to be equivalent to O3X’s /var/run/disk/by-id and to Linux’s /dev/disk/by-guid features.

What I’m missing is a FreeBSD equivalent to O3X’s /var/run/disk/by-serial feature, which identifies disks by manufacturer and serial number.  That’s more useful to me than GUIDs, since I can have a set of clue-deficient remote hands pull the disk and verify it by looking at the drive’s top label.  That method even works with dead disks; GPT labels survive only as long as the disk, and it’s often on dead disks that I care to have the correct disk identified, so I can replace it!
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