Fastest way to replace all drives in an array

[berta123]

Hello everyone!

I decided to build out a remote backup server for my unraid instance. I currently have dual parity with 12 data disks. My plan is to take all my existing drives and move them to a simple QNAP device and then use all new SAS drives in the array. The new drives are larger than the old in aggregate but there are less drives (replacing 12tb drives with 18tb)

 

So my question is how can I most efficiently migrate data from the old drives to the new and remove the old drives from the array? Keeping Parity throughout the process is nice, but not a strict requirement. I seem to have found 2 ways online, replacing drives 2 at a time and rebuild parity, or transfer data off the old drives and zero them out. Is there a 3rd way given the large number of disks? Which of these would be faster? 

[itimpi]

One point that does not seem to be mentioned is whether you need to keep all the data online and accessible the way it is currently during this process as that might make a difference to the answer.    Also since with that amount of data will take a significant time to migrate do you have any views on how you would view speed v availability of the data.

[berta123]

It’s fine for it to be offline. 

[itimpi]

Do you have any free connections for mounting additional drives?    You could format and mount the new drives using the Unassigned Devices plugin and then copy data from the existing drives one at a time across to new drives.    At the completion of this you could then use New Config  tool to create a new array of just the new drives taking advantage of the fact that Unraid will leave there contents intact as they are already partitioned/formatted correctly for Unraid and then add the new parity drives to build parity based on the new set of data drives.    The advantage of this is that you keep the old drives and their contents intact until you have the new drives up and running.

[berta123]

Yes I have plenty of connections. In fact all the drives are in the server right now as I do a pre-clear on the new drives to test them. 
 

Is there a particular command I would use to copy over to the new drives? Would I be able to change from xfs to ZFS for the array drives in the process? Also does this work if I need to reduce the total number of drives? 

[lixe]

I plan to do the same. Currently I have 3x4TB and want to replace them with 2x16TB.

 

My plan would be as follows:

 

1. add a 16TB disk and configure it as second parity disk
2. remove the 4TB parity disk and use only the 16TB disk as parity
3. add the second 16TB disk to the array (preclear before, so that the parity disk stays in sync)
4. move all data from both 4TB disks to the new 16TB disk
5. finally shrink the array to remove the two 4TB disks

 

Should that work?