Rob is right, I was also wrong above, you can't change filesystem for an emulated disk, what you can do, and I believe what the OP did is option C I listed above:

 

Array is stopped with a disabled/emulated disk, assign the replacement disk, now you can change the filesystem, start array, the rebuild will begin but the disk will be unmountable, user formats the disk.

 

How about adding a pop-up warning like the ones v6.3-rc now has for some other operations? Leave the current checkbox but add a pop-up that "formatting a disk is never part of a rebuild and after that it can't be recovered by parity" or words to that effect.

How about adding a pop-up warning like the ones v6.3-rc now has for some other operations? Leave the current checkbox but add a pop-up that "formatting a disk is never part of a rebuild and after that it can't be recovered by parity" or words to that effect.

That and disabling the option to change the fs type on a disabled disk / assigned but not rebuilt disk.

 

But make the pop up more generic because there are many other instances where users have inadvertently pressed the format button.

I suppose the format part is how I screwed up but in my experience with every OS I've worked with, a drive has to be formatted to be of any use.

This is due to a misunderstanding of "format". Format means "write an empty filesystem (of a certain type) to this drive". That is what it has always meant in every operating system you have ever used. There are other operations that are involved in preparing a disk, such as creating partitions. Sometimes all this is combined in user interfaces, but in the end, format always ends up with an empty filesystem.

 

I don't really understand how this happens either, but this is not the first case. The only time I have ever seen unRAID offer to format is when it doesn't recognize a filesystem on the disk.

I think there were 2 mistakes made here: 1. the filesystem on a replacement drive was changed to something different than original, and 2. it was formatted.

 

(I have lately been switching existing data drives from ReiserFS to XFS and so I have done this process several times now. When you stop the array, change the filesystem, and restart the array, there is no choice to rebuild data, it only gives an option to format "unmountable". After the format, the space on that drive is 100%.)

 

Notice that nowhere on the replace drive process does it say to format:  https://lime-technology.com/wiki/index.php/Replacing_a_Data_Drive

 

If you assign a new (precleared or unformatted) drive into the old drive's slot and start the array, it should ask to rebuild data on the new drive. But if you have made mistake #1, I think the only option provided then is to format it. If you then make mistake #2 (inevitable), this is irreversible.

 

This does seem like a good opportunity for a built-in warning.

 

III_D

This mistake can happen after a faulty disk is replaced by a new disk and before a data-rebuild is started. A user can change the file system at this point.

 

I propose to disable the file system selection when a data-rebuild is pending.