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adding new larger drives and replacement safely

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My server is a dell r720xd, so 14 drive bays (has 2 2.5in bays on back). 2 are for ssd cache and 1 is an ssd for VMs, which leaves 11 3.5in bays for drives. As you can see in the picture, really out of space. With 16tb exos drives still being new enough that they are ~25% more expensive per tb and haven't really seen trends yet on the off chance that there was a defect with drives, was going to go with 14tb exos. To use larger drives, I need to have bigger parity. Below is the proposed plan as for best steps to take based on what I've seen around, but guessing it has some steps that are not needed or other streamlining methods...and also last step is where not sure best method that is also safest.


Maybe I'm just being paranoid about the 16tb exos. If so, let me know to buy them for parity for an extra ~$150 each. As using the larger parity now will allow me to add 16s when they come down in price soonish (hopefully). In the long run, this seems like a better idea, just don't know if can really trust them yet. With 16s, step 3.2.3 would bee getting 2 16s now for parity, then somehow recombining the 3x6tb and 2x12tb exP into data section adding 16s as needed with whatever the proper swap methods are. Am I being paranoid? And now that this paragraph has been added it is clear that I have an idea of what end result needs to happen but no idea how to really get there easily. If am being paranoid let me know and will adjust below to be about 16 not 14.


current array:

  • 2 x 12tb P
  • 3 x 6tb
  • 4 x 12tb
  • 2 x OPEN
  • 2 x 1tb cache
  • 1 x unassigned ssd for VMs  { *** looking at currently is use ones, only 1 is on the ssd and the rest are on one of the shares. if need be, i can move that vm to the share to remove the ssd to open up another slot during this procedure and then move it back later *** }


  1. prepare new drives {0 open bays}
    1. use 2 open bays for new 14tb
    2. run preclear 3 times (iirc 12tb took about 2 days for each clear so looking at a week of testing, but being the new parity drives I want to make sure they are good, unless 3 times is now overkill)
  2. "fix" parity {2 open bays}
    1. take 2 12tb parity drives out and set aside
    2. assign 2 14tb as parity and start parity check (unless doing a bit copy from the 12tb P would be better)
  3. add exP storage {0ish open bays depending on step 2}
    1. put thee 1 12tb exP drives back in
    2. ????????
      1. this is where it seems to have more variance depending on where I look between data moving and parity rebuilding (and some unraid tools). I want to add the 12tb exP to the array for data, add 14tb drives and remove 6tb ones.
      2. it seems like there are 3 main methods people are taking here
        1. move data off 6 and onto 12, remove 6, add new
        2. add 12 to array, build parity, swap 6 with 14, build parity, repeat swap build as needed
        3. swap 6 with 12, build parity, add new
      3. have not ordered the drives from amazon yet, but if preclear is going to take a week, will probably order 2 and then when they are almost done order the data drives (probably go ahead and order 2)


new array:

  • 2 x 14tb P
  • ?? x 6tb ---> eventually 0
  • 4 x 12tb
  • 2 x 12tb - exP
  • ?? x 14tb ---> eventually 2
  • 1 OPEN (not required, but makes it easy to preclear a new drive before adding or slot in some unassigned drive for whatever reason-probably need to add an expansion bay-or whenever i add a 3rd ssd to cache)
  • 2 x 1tb cache
  • 1 x unassigned ssd for VMs



Feel like im making this more complicated than it needs to be, or all those rebuilds are just a part of the unraid experience that hadn't really had to deal with yet (only had the server for about a year). Thanks for the help.

out of space.PNG

Edited by Cull2ArcaHeresy
added note about VM ssd

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First off, I know nothing about drive quality, so the question of which drives are good... I got nothing.


Your overall plan makes sense to me, replace the 2 parity drives first, since they need to be the biggest. After that I would go for the "rebuild drive" option instead of the "moving data" option. This allows you to drop a smaller drive back in, should a rebuild fail, and not lose data, as well as being the quickest option (that I know of). Hopefully this helps.

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Replace your parity drives and rebuild parity. Take the 2 parity drives and use to replace any of the data drives. You can replace 2 drives at one time and they both will rebuild at once. Saves some time.

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