First post to UnRaid forums.

Currently have 36 bay Supermicro server with 35 drives installed:

2 - 6 TB parity drives

27 - 1 to 6 TB data drives assortment totalling 84TB

2 - 1 TB cache drive pool

4 - 3 and 6 TB unassigned drives

I am starting a changeover to remove all my older 1 and 2 TB drives from the system (all are over 10yrs old)

Started process by changing Parity drive 1 to a 20 TB disk.

Next step is to shrink Parity drives from 2 to 1

Last step is to remove older 1 and 2 TB disks

What is the best way to remove the older disks with the least amount of parity rebuilding and maintain data integrity?

Move all of the data from all of the drives you want to remove to the ones you want to keep. (You didn't say if you have enough space on the remaining larger drives for all of the data on the drives to be removed...) This will preserver parity until the move operation is completed.

Then remove the drives and rebuilt parity. (Personally, I would run a parity check before I did this but I tend to be a believe in Mr. Murphy's laws regarding bad things always happen which cause the most damage...)

If you don't have enough space on the larger drives then you need to plan a series of moves/drive_replacements to achieve that.

A couple of personal observations. When done, I would want between 20 and 25% free space on the array. Otherwise, you will shortly be looking at how to expand the array. Next, I would question the leap from 6TB to 20TB for parity without indicating that you are immediately adding one or more 20TB data disks. I would look more on the order of 12TB and considering a second parity disk of 12Tb if the number of data disks in the array will be more than, say, eight disks. (With a 20Tb parity disk, parity check times will be well above 40 hours!)

Edited July 15, 2025Jul 15 by Frank1940

I am sort of future proofing, I have far too many older smaller drives in the array and want to reduce the number of drives as well as reduce overall power consumption but leave the array size constant for now. The array is currently only ~ 40% occupied. As I need new drives I will likely get bigger drives (16 - 20TB). I realize the parity size is large and the parity rebuild on 20TB took about 65 hrs, but I schedule parity check every 3 months and pause so it will likely take 1-1/2 weeks every 3 months to do (probably not that long with my max array drive as 6 TB right now though). I do have enough space to move all the files from the disks I want to remove to disks that will stay. My first attempt was to copy from a drive I want to remove to a drive I am keeping while still in the array operating, but I think I need to move not copy if I want to take this drive out of the array?

24 minutes ago, medmad said:

, but I think I need to move not copy if I want to take this drive out of the array?

You can't copy if the file is in a 'Share' because you will then have two files with the same name in the share. By the way make sure that your copies are disk-to-disk and not disk-to-share! you risk data loss if you do!!!

Even if you copy a file (say, Mash.mkv) from disk 12 to disk 5 cp /mnt/disk12/movies/Mash.mkv /mnt/disk5/movies/Mash.mkv You will now have two copies of that mkv file in the movies Share. This can cause real cockpit confusion later. You want a move operation which is often a copy-then-delete sequence.

Oops, didn't think of that. When I did the copy I did it in MC and the new drive was not available on the shares as I had not configured the share properly yet. I just deleted the content on the destination drive that shares was not aware of yet. I will use file manager in unraid to do the renmove of the files I want moved.