I currently have a Hornettek Enterprise Quad bay USB3 JBOD hooked up to a Mac Pro running Mavericks. It has two 3TB disks which are mirrored (RAID 1 using Disk Utility) and contain a mixture of personal data and media shared by the Mac Pro to an AppleTV.

I’m fast approaching 3TB of data and need to consider expanding, most likely with another two 3TB drives to the JBOD.

Once I’ve added two new disks to the Hornettek JBOD I will have 4x3TB disks. Using software RAID under OS X Mavericks, what is the best option to ensure redundancy and disk usage?

A few years ago I used an OpenIndiana server to RAID-Z a few disks together, but gave that up for the simplicity of OS X only. But I guess it’s something like RAID-Z that I want, only a stable OS X solution.

  • Your question is somehow inconsistent or I don't really understand it: You are asking for expanding a JBOD, but actually your are using a Software RAID1. Or does JBOD refer to the Hornettek ... JBOD? – klanomath Aug 3 '15 at 12:42
  • @klanomath sorry, I am planning on adding two more disks to the Hornettek JBOD and want to know the best way to utilise 4x3TB disks using software RAID in OS X Mavericks. I’ll update the question also. – forquare Aug 3 '15 at 12:50

First of you you cannot expand a RAID-1 (Mirror). If you want to make a larger RAID array you will have to back up the drives and recreate the RAID array in a different configuration.

Once you have done that you have several configuration options with 4 disks. A quick google of types of RAID will show that... However if it were me I would set up the 4 3TB drives as a RAID-5. Yielding 9TB of disk space. That makes all disks in the enclosure part of the same array.

There is a problem with that though. Disk Utility will only give you RAID-0 or RAID-1 (non-redundant stripe or mirror). Which means that you would have to purchase a third party RAID utility to do RAID-5. There are a couple out there and I have heard they do a good job. Depending on your budget that would work well.

Your other (no cost) option is to put the other two disks in your enclosure and just set them up as a second RAID-1 array. It won't give you the speed or as much space as a RAID-5 (6TB total usable space) but it will work just fine and show up on your Mac as a second volume.

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  • Thanks for the information Steve. I’m looking at presenting one volume that all four drives are a part of, and I was pretty sure I’d have to break up the existing RAID configuration to recreate. Not being sure of the kind of price such software costs (I’m sure there is a great variety), I’m not sure on a budget yet (though I would guess tens of £ rather than hundreds). I’ll have a search around for such software, or if you know of any reputable utilities it would be useful to hear of them. – forquare Aug 3 '15 at 14:16
  • @forquare The only software capable of doing RAID 5 I know of is SoftRaid (123 £) – klanomath Aug 3 '15 at 14:55
  • I have no personal experience with 3rd party RAID software, though the name SoftRAID does come up a lot in these discussions... – Steve Chambers Aug 3 '15 at 16:02

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