I recently purchased a WD Thunderbolt Duo, which has two 4 TB drive, now running in RAID 0 with Apple Software RAID.

My question is simple, if I am to get another Thunderbolt Duo next year, is it possible to add the two additional disks to RAID 0 without going offline? (Copying files out, and then destroy the RAID set, build the new RAID set and then copy the file back.)

  • So you currently have Disk1 + Disk2 = RAID Set1(striped)
  • You want to know if you can RAID Set1 + Disk3 + Disk4 = RAID Set(striped). Disk Utility doesn't allows this.
  • You can however have Disk3 + Disk4 = RAID Set2(striped) and then use a symbolic link or mounting to move the set to a location that is convenient for you.
  • You would think that you could Disk1 + Disk2 = RAID Set1(striped), Disk3 + Disk4 = RAID Set2(striped), RAID Set1 + RAID Set2 = RAID Set3(concatenated). Unfortunately it doesn't look like Disk Utility allows this.
  • Or you do what you mentioned earlier, and backup everything then blow away your existing RAID Set to create a new one with all 4 disks.
  • I see. But in theory, is that doable? – Shane Hsu Jul 25 '13 at 15:49
  • I am actually trying to move from D1+D2 to D1+D2+D3+D4 – Shane Hsu Jul 25 '13 at 15:50
  • I mentioned this in bullet point #5. You can do this only by destroying the existing data. So backup everything on D1+D2, and then create a RAID0 with D1+D2+D3+D4. – Michael Yasumoto Jul 25 '13 at 21:31
  • Is there any other RAID solution, possibly not by Apple, that can do this on-the-fly? – Shane Hsu Jul 27 '13 at 4:44
  • Different vendor RAIDs are usually not compatible. You can't just take two disks in an Apple software RAID and add them to a Linux software RAID or a Promise hardware RAID. Since D1+D2 are already in an Apple software RAID, if you care about your data, then you will use Apple's software to manipulate this RAID. Changing halfway through is dangerous. – Michael Yasumoto Jul 27 '13 at 16:27

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