Backup the USB drive


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The most important thing to have backed up is your license or .key file.  Since the license file is tied to the GUID of your USB drive, though, having it backed up is really only useful if the contents get scrambled but the stick itself is fine.  There's a bit of debate as to whether backing up the rest of the USB stick is useful.  Some feel you should just download the latest unRAID files and reconstruct, others like the idea of a backup.  If you do perform a backup of the USB stick you need to be thoughtful in the event you ever do a restore.  If the array is in a different state than when you did the backup (running or stopped, disks added or removed, etc.) then simply copying all the files back is not the right solution.

 

Personally I backup my USB stick each time I update unRAID.  I stop the array, backup the entire contents of the USB stick, and then perform the plugin upgrade.

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The risk of using a backup flash is significant. I'll explain the issue below, but if there is any question whether your backup is current, delete the file called super.dat from the config folder. On boot you'll have to reassign the drives and either trust parity or rebuild it. But your Docker templates and various other settings should mostly be accurate.

 

Super.dat is a busy little file and the most important for the NAS features. It does two important things - It maintains the list of what drives are assigned to what slots. And it also maintains whether the array is stated or stopped. (If you ever backup the flash, do it when array is stopped, otherwise if you restore with the backup, unRaid will detect a dirty shutdown)

 

But the important updates are when your disk configuration is changed. Say you buy a new parity disk and move the current parity to the array as a data disk. And sometime later you use a backup stick from before the parity upgrade. Your drive configuration will revert to the old parity being parity again. Starting the array will instantly corrupt that disk. And worse still, if the backup was taken while the array was started, starting with he array will trigger a parity check. Newer versions of unRaid run a non-correcting check, but older ones run a correcting check. And a correcting check will obliterate any chance of recovering data on that disk.

 

So that's the basic risk, in many different flavors. Restoring a disk with an old super.dat disk configuration is infinitely worse than rebuilding the flash from scratch from perspective of preserving your data!

 

The version of unRaid installed is less of an issue unless it is many versions behind. And this is more easily corrected than a corrupted disk.

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If you keep a backup of your license file, then contacting limetech is automated and you have almost no downtime. If you put your dead USB stick's license key file on the new stick, it will walk you through transferring the license to the new stick automatically.

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On 7/11/2017 at 8:45 AM, bjp999 said:

But the important updates are when your disk configuration is changed. Say you buy a new parity disk and move the current parity to the array as a data disk. And sometime later you use a backup stick from before the parity upgrade. Your drive configuration will revert to the old parity being parity again. Starting the array will instantly corrupt that disk. And worse still, if the backup was taken while the array was started, starting with he array will trigger a parity check. Newer versions of unRaid run a non-correcting check, but older ones run a correcting check. And a correcting check will obliterate any chance of recovering data on that disk.

It should be noted that the USB Backup part of CA's Appdata Backup Module does not backup the super.dat file (actually, it does but renames it)

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Just now, Squid said:

It should be noted that the USB Backup part of CA's Appdata Backup Module does not backup the super.dat file (actually, it does but renames it)

 

I did not know that - but now that I do I will recommend it and start using it. There is a lot more to save on the USB stick than in the old days.

 

Thanks!

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