I am running FreeNAS-9.3-STABLE-201512121950 from a USB stick in VirtualBox on a Mac Mini Server (late 2012 - Macmini6,2) running OS X El Capitan. Quad-core i7, 16G RAM, with 8G and 2 procs devoted to the FreeNAS VM.

I have multiple external hard drives (SATA and SSD) connected via USB3.0, which I am using for 2 separate storage pools consisting of virtual hard disks (.vmdk) on these individual physical drives.

  1. /mnt/ZFS (RAIDZ3 - 6x500G + 64G L2ARC SSD cache) - built for redundancy and important stuff, uses lz4 compression
  2. /mnt/Media (Various size drives, all striped + 64G L2ARC SSD cache + 8G ZIL SSD log) - built for streaming media, no compression or redundancy.

I have successfully installed and setup the Plex Media Server plugin, which uses the jail root /mnt/Media/Jails. It has the full amount of the /mnt/Media Dataset available to it without me allocating storage to this jail.

Now, what I want to do is to install the Crashplan plugin, but I realize that there is only a single jail root, which is not located on the preferred Dataset (/mnt/ZFS). I am wanting to backup important stuff with this plugin, and it should be separate from my Media dataset.

I'm having trouble wrapping my head around the whole directory/file structure and implications of jail/plugin deletions if anything were to go wrong.

The only things I can think of at this point would be one of the following 2 options:

  1. Add an additional Dataset specifically for jails/plugins, and set the jail root inside this new Dataset.
  2. Set the jail root to /mnt/ZFS/Jails for redundancy

Questions regarding #1:

  • Would the new Dataset for Jails need to be redundant if I were to install the Crashplan plugin and allocate /mnt/ZFS to it in order to back that up to the cloud?
  • After assigning storage to this Jail dataset, if I delete that Dataset, will it also delete the files from /mnt/ZFS that are assigned to it -- and to prevent this, could I just un-assign /mnt/ZFS to the Jails Dataset and/or Crashplan plugin?

Questions regarding #2:

  • If I assign storage from /mnt/Media to a Plex Media Server plugin stored the jail root of /mnt/ZFS/Jails, what would happen if I lost a drive from /mnt/Media? Would it also corrupt the /mnt/ZFS Dataset?
  • Would the entire storage of /mnt/ZFS be made available to /mnt/ZFS/Jails/plex_media_server1?

My goal is to keep these 2 datasets separate, but to be able to install plugins on each one. I am totally at a loss. Any help or advice would be appreciated at this point. I have read the documentation, but it's really not helping with my particular situation, as far as I can tell.

1 Answer 1


Since this question has not gotten much attention, and it doesn't seem to be as much of an issue anymore, I am going to try and answer it myself from what I have found via trial and error.

Rather than offering a bounty on this, I seem to have come up with a working solution, but if anyone can offer a better answer than this, I will gladly choose their answer.

  • I added a Dataset /mnt/ZFS/jailroot so that my jails would be redundant.
  • I added storage from /mnt/ZFS/Media to the PLEX jail under /media.
  • I added a Dataset /mnt/ZFS/NAS for important files that require redundancy.
  • I created a Crashplan jail under the /mnt/ZFS/jailroot Dataset
  • I added storage from /mnt/ZFS/NASto the Crashplan jail under/media`.

Nothing seems to have changed for the worse, but from what I gather from the FreeNAS documentation, this is how it should work:

  • Adding storage to a jail is only adding pointers (sort of like symlinks) to those files from the associated Dataset, so it doesn't actually increase your storage use
  • The actual jails which have these Datasets assigned to them don't interpret the files as symlinks, but as actual files, so deleting them from the jail will actually delete them from the filesystem.
  • This should mean that if I delete the Plex jail, it will also delete everything inside that jail under /media, which includes the /mnt/Media Dataset assigned to it, so I would first need to un-assign that Dataset from the jail before deleting the jail
  • However, I think in the latest versions of FreeNAS, there are fail-safes in place that prevent this behavior from occurring.

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