I just found out about unRaid and just got it up and running. Before I do the pre-clear I want to know if I can later decrease the drive sizes if a drive fails? Lets say I have three 1 terabyte drives and I later want to decrease one to 500gb will that be ok or am I only allowed to go up? I know that the parity drive has to be equal to or great than the highest drive. Which i'm fine with.

 

 

You cannot directly "replace" a 1TB drive with a smaller one.  You can install a "new" 500GB drive, copy files off the 1TB to the new 500GB drive (if they will fit), and then remove the 1TB drive.

If you have three 1 terabyte drives, you can add a 500 gigabyte drive. Which is not what you asked, but part of the answer.

 

Drives already in the array are typically not removed, only rebuilt. A 1 terabyte drive can not be rebuilt on a 500 gigabyte drive.

 

What you are describing is basically building a new array, which is possible with unRAID because of the special property that each drive is a complete filesystem.

 

When the array is built with three 1 terabyte drives, the capacity is 2 terabytes. This is the combination of two 1 terabyte filesystems, protected by 1 terabyte of parity. Change one of the 1 terabyte filesystems for a 500 gigabyte filesystem, the capacity is 1.5 terabytes.

 

So the trick in replacing a 1 terabyte drive with a 500 gigabyte drive is putting all the files from the 2 terabyte array on the new 1.5 terabyte array. If it will all fit, you can do it.

 

The array must be healthy, no failed drives.

 

When you build your array with three 1 terabyte drives, there will be disk1 and disk2. Adding the 500 gigabyte drive will make disk3. Use the normal disk add procedure.

disk1 is a 1 terabyte data drive with X bytes of files.

disk2 is a 1 terabyte data drive with Y bytes of files.

disk3 is a 500 gigabyte data drive with Z bytes of files.

X + Y + Z must be less than 1.5 terabytes.

As a new drive, disk3 should have Z = zero.

X + Y must be less than 1.5 terabytes.

To remove disk2, copy the files from disk2 to disk3. If needed place some of the files on disk1.

Once all of the files have been copied, build an array with disk1, disk3 and a 1 terabyte parity drive.

Thanks guys. That's pretty much what I was looking for.