Hi, I am considering move from openmediavault to unraid. however I have 21 hdds range from 0.5~4TBs in ext4 file system almost filled with data.50GB of free space in average and  I do not have any other free hard drives. Is there any easy (and safe) way for me to migrate my data to unraid if I purcharse a pro license? Thank you!

Edited January 6, 20206 yr by ifdog

You need at least one disk to start an array with, and Unraid must format any disk it will use in the array or cache pool. If you can empty one of those disks, preferably one of the larger ones, you can use it to start, then mount one of the other disks with the Unassigned Devices plugin and copy its files, then add it to the array, repeat.

12 minutes ago, trurl said:

You need at least one disk to start an array with, and Unraid must format any disk it will use in the array or cache pool. If you can empty one of those disks, preferably one of the larger ones, you can use it to start, then mount one of the other disks with the Unassigned Devices plugin and copy its files, then add it to the array, repeat.

So the procedure is :

1, I add the UD plugin.

2, I try to empty a larger hdd ,and add it to the array, without adding a parity or a buffer,then start the array.

3, I copy data (in command line with cp or midnight commander )to fill the array to empty another hdd,

4, I stop the array, add the newly emptied disk, without adding a parity or buffer, and start the array.

5,I loop over 3 and 4 till all hdd is added (but still no parity or buffer).

6,Then I need a disk as parity and it should be the largest one in their volume.

Am I understanding it right?

Edited January 6, 20206 yr by ifdog

That's basically it.

 

But I have to ask, do you have another copy of anything important and irreplaceable? Parity is no substitute for a backup plan.

Yes I do.  some of my data was placed in a mirrored software RAID managed by madam under linux. you mean Parity is not as safe as Raid1 ,do you?

Raid1 is not a backup either. You need your data offsite for it to be backup.

Plenty of ways to lose data that don't involve a failed disk. User error is a lot more common than disk failure, for example.

2 hours ago, ifdog said:

Yes I do.  some of my data was placed in a mirrored software RAID managed by madam under linux. you mean Parity is not as safe as Raid1 ,do you?

The opposite - Raid1 is nowhere near as safe as Unraid parity!    With a typical RAID if you lose more disks than you have redundancy you lose everything.    On Unraid in such a scenario you only lose the data on the failed disks - all other drives are still accessible as each drive is a discrete file system.   This was one of the reasons that made me switch to Unraid in the first place.

 

However as several previous posts have mentioned any data that is important should be backed up off the server, and preferably have an off-site copy as well.   It is always possible (albeit unlikely) to have some sort of catastrophic failure that was not catered for.

 

 

On 1/6/2020 at 4:03 AM, ifdog said:

Yes I do.  some of my data was placed in a mirrored software RAID managed by madam under linux. you mean Parity is not as safe as Raid1 ,do you?

Others have mentioned how Unraid parity is superior to RAID-1 (to be exact, RAID-1E but that's academic).

 

What I'd like to point out is you are probably confused about backup, RAID mirror and Unraid parity.

• A backup is a complete, independent and redundant copy of your original data.
  • Complete = you don't need anything else to recover the data other than the copy itself
  • Independent = operations not performed directly on the copy does not affect the copy
  • Redundant = the copy is only accessed if (a) data needs to be recovered from the copy and (b) the copy needs to be updated
• A RAID-1 (i.e. mirror) is NOT a backup since it fails the independence and redundancy tests.
  • When something changes the data, the mirror copy is automatically and immediately changed too.
  • Both mirrors are equally likely to be accessed in regular uses.
  • (Just think for example, you accidentally delete your wedding photo, can you recover it with a RAID-1 mirror? Answer is no because the mirrored copy also deletes the photo as soon as the original is deleted).
• A (Unraid) parity is NOT a backup because it fails the completeness test i.e. recovering data requires data from other disks to reconstruct the missing piece.