Suppressing the annoying pop-up
From OpenZFS on OS X
As of version 1.3.0, you should not see the message "The disk you inserted was not readable by this computer" unless one or more devices in your pool is a partition with a type code specifying a file system other than ZFS. The correct partition type GUID for OpenZFS on OS X is "6A898CC3-1DD2-11B2-99A6-080020736631," which may display as any of the following, depending on what tool you're using:
- bf01
- ZFS
- EFI_USR
- Solaris /usr & Mac ZFS
- 6A898CC3-1DD2-11B2-99A6-080020736631
The easiest way to correct the partition type is to use gdisk which is distributed via Homebrew as the formula "gptfdisk" or via SourceForge as a pkg installer. The gdisk function for changing partition type is "t," as explained here.