[6.11.2] Best way to add 2nd parity AND replace 2 data disks for array?

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Hi all! I've had 3 8TB drives sitting around for a while, and I would like to finally integrate them into my UnRaid Array as safely as possible, while not taking more steps than needed.


Since I'm about out of SAS ports (I have onboard+card) I'd rather pull 2 of my 4TB drives and replace with the 8TB, and add the 3rd 8TB as a 2nd parity. I've done the process at https://wiki.unraid.net/Shrink_array#For_unRAID_v6.2_and_later before, years ago. I've already used unBalance to move data off my designated drives for the swap.


So, my questions are:

  1. Is that "shrink array" process above still the best for swapping out data drives?
  2. Is there a good process for doing the above and adding 2nd parity drive at same time? Or do I need to do them one at a time?
  3. If I do need to add 2nd parity separate from swapping data drives, should I do the 2nd Parity first?


I am OK with taking my time to do it "right," and just wanted to know if there's a better way that I'm just not aware of. Thanks for the time!


NOTE: Yes, a few revisions behind; unBalance has, of course, taken time to move the files and before that I got busy with work. I plan to upgrade to latest before doing anything further.

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  • Solution

No point in emptying drives or shrinking the array to replace disks. Just replace and rebuild.


If your current parity is as large as the new disks then no problem. If not then you need to replace parity first. Each parity has to be at least as large as the largest single data disk.

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45 minutes ago, trurl said:

No point in emptying drives or shrinking the array to replace disks. Just replace and rebuild.


If your current parity is as large as the new disks then no problem. If not then you need to replace parity first. Each parity has to be at least as large as the largest single data disk.

New parity drive is same size as current, so it sounds like I'm just going to add everything and then rebuild, and that's fair enough. Thanks for the information!

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56 minutes ago, raqisasim said:

add everything and then rebuild

I wasn't talking about ADDING disks, but replacing and rebuilding each one at a time, or if you add and build parity2 first you could replace and rebuild 2 at once.


Since you were thinking about shrinking the array I am still wondering what you intend to do.


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27 minutes ago, trurl said:

If the new disks are intended to replace empty disks, then New Config with all the new disks in place including parity2, rebuilding both parity, and formatting the new data disks is probably the fastest.


But still unclear what your situation is or what idea you have about how to proceed.


Attach diagnostics to your NEXT post in this thread.

Hi. I have to apologize on multiple counts. I upgraded, shut down the server, and left home to spend time with family, so won't be able to add the diag file until I get back Monday. If you want to ignore the rest of this reply until I can add the file, I understand.


I say this because I clearly am causing frustrations I do not mean to, by not explaining fully and using incorrect terms instead of fully documenting my idea. Again, my apologies for that, and I will ensure I upload the requested diagnostics ASAP upon my return to my home. That said, I ask for your patience as I attempt to clarify my situation and goals:


1) I have an Array with 1 8TB parity drive, currently, and a mix of 4 and 8 TB drives, a mix of SAS and SATA, for the data drives.

2) I have 3 8TB SAS drives, not installed in anything currently, that I would like to use in this Array, in the following ways:

    2a) Use 2 of the 8TB drives to replace 2 of my existing 4TB drives, and

    2b) Use the last 8TB drive to become a 2nd parity drive; it will not replace any existing drive

3) I have one more SAS connector for a drive, so cannot connect two more SAS drives to the server/Array. It will, obviously, need to become the connector for the 2nd Parity.


To hopefully clarify why I referred to shrinking the array for the above process -- as I said in my original post and above, I used that "shrink array" process, from that wiki page of "shrinking the array," to do this a few years ago, successfully. That time, I "shrank" the Array by three 2TB SAS data drives, physically removing said drives, then adding three 4TB SAS drives into the same Array. I did it in this fashion because that wiki page says explicitly that "This method is best if you are removing more than one drive" which is my plan, per above, and also given connection limitations. That is why I linked to that page, and talked about shrinking the array.


The idea I have this time is to do 2a) above by "shrinking" out the two 4TB SAS drives currently attached and in the Array, physically removing the drives, and then adding the 2 new 8TB drives in. Along with, of course, adding a 3rd 8TB drive for a 2nd Parity, as I mention above.


And I'm trying to ask if there's a better approach that using that wiki page, esp. given the age of that wiki page and the goal to add the 2nd Parity. Given that your guidance leverages using "New Config" once the new drives are added, which aligns with Step 4 in the wiki documentation, I suspect, at the end of the day, it is still the right procedure, and this confusion was due to my clumsy words more than anything technical.


I hope this clarifies my goals w/o adding more frustration to the discussion. Thank you, all, for your time and attention, and again I shall add the diagnostics as soon as possible.

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Sounds to me if you could do what you want in 2 steps:

  • use the spare connector to add the 8TB parity2 drive and build parity2 so you are running with dual parity.
  • use the Parity Swap procedure to replace 2 existing 4TB drives with 2 8TB drives.   With dual parity these can be done in parallel.   I would recommend keeping the removed 4TB drives intact until the Parity `swap process has completed and the 8TB drives are now successfully showing what was on the removed 4TB drives just in case anything goes wrong.
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8 hours ago, itimpi said:

use the Parity Swap procedure

Don't see what parity swap has to do with it. He isn't changing parity1, just adding parity2 and replacing 2 data disks.


Shrink array was the wrong path to go down also to simply replace 2 data disks and add parity2.


@raqisasim Rebuilding data to replacement disks is the whole point of parity. Why go to all the trouble to move data, shrink array, then add disks when you can just rebuild the data to the new disks?


I only mentioned New Config because it seemed like he had already emptied the disks to be replaced, in which case he could simply do a new array that included parity2 and the new, unformatted replacement disks, build both parity, and format the new disks.

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