I've been migrating all my drives to XFS, slow going, but thus far no problems that weren't caused by me and explainable.  Until yesterday.

 

But this one was interesting.  I was moving all the files off of an almost full 4TB reiserFS drive onto a newly formatted XFS drive, also 4TB, using MC inside a screen session.  And when I say the drive was almost full, the reiserFS drive had maybe a few megabytes free.  But everything I've read in the forums about migrations says that after formatting with XFS a drive will at least have the same amount of space on it for files, and I think some people have claimed it might even have more. 

 

It seems that the very last file on the drive to be moved was a bluray iso image of about 30gigs in size.  And it got stuck moving about 3/4 of the way through.  Via Windows explorer I moved 10gigs of files off of the destination drive onto the hard drive of my desktop pc, told MC to try again and it worked.  Then through windows explorer I moved the same files I just moved off, back on to the destination drive, and it worked.  Unraid gui shows a few megs free on the drive, unfortunately I didn't take a screen shot or write down how much free space was on the ReiserFS drive before the move, but I think the space is pretty similar. 

 

Anyone have any idea what might have happened here?  Not a big deal because all files involved have a safe and secure home now, it was just weird. 

Not clear mc was the culprit. I think it is really just a front end for normal linux command line things like mv, cp, etc. Probably if you had tried to do it from the command line in exactly the same way mc was doing it you would have had a similar result.

 

I used mc in screen when I converted to XFS but all of my drives had plenty of space.

I do not think it is safe to assume that XFS will always use no more space than ReiserFS. I think there are all sorts of factors that come into play, and with a disk so full you can easily hit a case where this is not true. 

There have been reports both ways r.e. which system uses space the most efficiently -- I think it simply depends on the specific characteristics of the files you're copying.    If your Reiser disks are VERY full it's even possible that you won't be able to get all of the files onto the same size XFS disk.

 

As for what specifically happened in the case you outlined ... are you sure it was "stuck" ?  ... i.e. did you wait a reasonable length of time (5-10 minutes) to ensure it didn't pick back up?    Not sure how XFS behaves in the "very full" situation (reports are that it's better than Reiser) ... but Reiser disks can take a LONG time to do a write to a very full disk if you're writing the last few GB.