Enable Bitrot on Files: MV or CP?

So I want to make sure that bitrot protection is enabled on my files, I don't recall if I had it enabled on my shares before files were placed there. According to the documentation you can create a new copy of the file and this will create CoW data for the new file. Does moving a file with the mv command do the same thing, or do you need to use the cp command to create another copy?

I made a new share, mv'd the files between, then removed the old share. Do I need to do this again with cp instead or did mv handle my task?

rn_enthusiast
Mar 08, 2021
You can use "lsattr" to check if a file has CoW enabled or not.

Here my txt file does not have CoW enabled, denoted by the "C" in the end.
root@Databak:~# lsattr /data/Data-dump/MyFile_NoCoW.txt ---------------C /data/Data-dump/MyFile_NoCoW.txt
Here is what a file looks like, that has CoW enabled.
root@Databak:~# lsattr /data/Data-dump/MyFile_CoW.txt ---------------- /data/Data-dump/MyFile_CoW.txt
I don't think the "mv" command is enough to trigger CoW on a file that has previously been marked for No CoW - due to reasons that StephenB mentioned. I think you need to re-create the file - i.e. "cp"

But you can check on the files you moved :)

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StephenB
Guru - Experienced User
Mar 08, 2021
rhpot1991 wrote:

I made a new share, mv'd the files between, then removed the old share. Do I need to do this again with cp instead or did mv handle my task?

I'm not 100% sure, but I think you'll need to do it again with cp.

If you are moving from window file explorer, the move is turned into a copy/delete when you access the shares using normal credentials. But if you access the full data volume using admin credentials, that doesn't happen - only the metadata is rewritten.

When you mv using ssh on the NAS, it's like that second case. The mv completes much faster than cp will, but that is because the file data isn't being copied. The bitrot protection feature depends on BTRFS checksums (plus RAID parity), and if they were turned off when you uploaded the files to the NAS, a "true" mv won't create them.
- rhpot1991
  Guide
  Mar 08, 2021
  Everything from SSH, could do it via a network share but that would add network overhead.
  
  MV across shares, takes some time - not instant.
  MV within shares is instant. (note this was done after above, which may have created metadata?)
  CP within a share is taking forever.
  
  Hopefully someone from Netgear can chime in if an initial MV will create the metadata or not.
  - StephenB
    Guru - Experienced User
    Mar 08, 2021
    rhpot1991 wrote:
    
    Everything from SSH, could do it via a network share but that would add network overhead.
    
    MV across shares, takes some time - not instant.
    
    MV within shares is instant. (note this was done after above, which may have created metadata?)
    
    CP within a share is taking forever.
    
    Hopefully someone from Netgear can chime in if an initial MV will create the metadata or not.
    
    Please don't double-post. I replied here: https://community.netgear.com/t5/Using-your-ReadyNAS-in-Business/Enable-Bitrot-on-Files-MV-or-CP/m-p/2066796