PR4100 Volume 2 Raid change

Hi, I have bought a PR4100 8GB model with the intentions of upgrading the size as time goes on. I have quickly ran out of space so I bought 2-10 TB red drives and successfully rebuilt the volume after replacing each of the first 2 drives.

I had 2-4 TB red drives that I swapped into the second bays successfully so now I have 28 TB of storage.

I have volume 1 which is a raid 10 4 TB volume and I have volume 2 which is a spanning 20 TB volume.

My question is, how do I get volume 2 into a raid 10 configuration?

Thanks for the help.


Hello jab73180,

You can upgrade your drives to RAID 10 but won’t be able to use the complete storage capacity of all drives as the usable data area on each drive is equivalent to the capacity of the smallest drive.
If you use 2x4TB drives and 2x10TB drives, the usable capacity in RAID 10 would be 14TB. However, you can follow the steps provided in below article to upgrade RAID:

I am sorry, I should have clarified that volume 1 is already in Raid 10. I want volume 2 to be in the same raid 10 configuration.

The optimal operation of any type of RAID requires all drives in one RAID volume to have the same capacity. To answer your question you need to replace the two the 2 x 4TB with 2 x 10TB to end up with 4 x 10TB. The result will be one optimal RAID 10 volume with a capacity of 20TB. RAID 10 is faster than RAID 1, 5 or 6.

In your case, with 2 x 4TB and 2 x 10TB the WD system made a non optimal compromised RAID configuration.

Obtain a WD external USB storage drive. Use the WD PR4100 USB backups utility to backup all your data from NAS to USB. Disconnect the USB drive, attach to your PC, verify all your data is intact. If it is critical irreplaceable data, obtain a second external WD USB drive and repeat the backup procedure.

You now have two verified backups of your data. On the WD PR4100 delete all volumes and data. Power off. Remove the 2x 4TB drives, install 2x new 10TB drives - you now have 4 identical sized drives. Create one RAID 10 volume. It will have a user capacity of 20TB. Use the WD P4100 USB Backups utility USB to NAS to restore all your data.

Result: All data in one RAID 10 volume.

how about moving from RAID 1 to 10 on a four drive pr4100, can i do this without data loss? All drives are the same 10TB.


Your question is not clear, I think you’re asking if you start with two drives in RAID 1, add two new drives, then change RAID mode to RAID 10, can you do this without data loss? The answer is NO. All four drives will be formatted as RAID 10, thus, all data is erased from all four drives.


RAID 1 is made up of two drives only, while RAID 10 is made up of four drives. All the drives should be the same size for optimal performance and date capacity.

If you currently have two 10 TB drives in RAID 1 you will have a total of 10 TB useable data in one volume. For example, you could call it data 1 and map it as drive P:

If you add two more 10 TB drives you can create a second RAID 1 volume with 10 TB of useable data. All the data on your existing volume will stay intact. For example, you could call it data 2 and map it as drive Q:

The grand total would be 20 TB of useable data across two volumes = two mapped drives P: and Q: P: would have all your existing data and Q: would be anew empty drive.

If you want to all 20 TB in one volume you have to migrate to a 4 drive RAID 10 with data loss


you could migrate to RAID 5 and have a total of 30 TB in one volume / one mapped network drive without data loss!

Refer to answer 20862…

In any case, I would always backup my existing data to an external USB drive first. If it is critical data, I would backup to two different external USB drives before making any changes.


Thanks Tim, yes I have all four 10TB drive and moved from a bad pr4100 shell to a new one. It was supposed to copy the RAID 10 format but it moved to RAID 1.

All being said, can you advise on the best way to make backups to an external USB drive and then recover it post the move to RAID 10? I tried copying my entire file over to the USB but it didn’t complete due to a file name on one file?!

You mentioned in another post of using the USB Backup, I’ve attempted this from the MyCloud URL but it times out.

Thanks again for your help!