I can't replace a larger data drive with a smaller even if size of data will fit regardless?

[andyd]

I need to replace a 10tb with a 8tb. The former is a shucked drive that has issues which I used when a 8tb failed. I want to replace the 10tb with a replacement 8tb drive. Even though there is like 3tb of data on the 10tb I get an error that the drive must be larger. How can I swap these two?

[JonathanM]

Parity emulates the entire drive, not the data. You can't downsize a drive without rebuilding parity, so you will need to copy the data manually. Do you have a slot available to temporarily add the 8TB to the current array?

[andyd]

I can make due by taking a drive offline that I have outside of the array I use for other stuff.

 

What are the actual steps?

1. Add drive - should it be in the array?

2. Copy over the data using something like krusader

3. Take other drive offline

4. ? rebuild parity?

[JonathanM]

I'm unclear by what you mean by taking a drive offline, you originally said you have a 8TB ready to go.

 

If you have a physical and license slot available, you would add the 8TB to the array, it would be cleared and then formatted. You would then copy the data from the 10TB to the 8TB with rsync, mc, or whatever you want, after you are sure all the data is intact on the 8TB, you would set a new config and put the drives where you want them, replacing the 10TB with the 8TB. Make sure to take a screenshot of your drives before you start so you can put them in the correct slots when you do the new config.

[andyd]

Offline - I just meant that I needed to take a drive out that I use outside of the array in order to free up sata/power connectors

 

I got through this but wasn't expecting it to be such a long process (clearing drive, copying data, parity sync) compared to just replacing a failed drive of equal or greater size.

[JonathanM]

3 hours ago, andyd said:

I got through this but wasn't expecting it to be such a long process (clearing drive, copying data, parity sync) compared to just replacing a failed drive of equal or greater size.

Yeah, removing capacity from Unraid isn't easy. Very few people shrink their servers, adding capacity is much more common. Parity works across the entire capacity of all drives, it doesn't have any concept of data or full or empty drives.

[andyd]

Makes sense. It made it harder to deal with since I had to remove a drive in order to go through the process but it's a reminder I need to upgrade at some point too