Restoring Data From Different Drive Size

I have an 8TB Mirror Gen2 that was running RAID as dual 4TB drives. One drive failed but the data is still on the mirror drive. I decided to use the opportunity to upgrade capacity and bought two 8TB drives rather than replace the failed 4TB.

I was later told you can’t run a 4TB with an 8TB and copy the data, which was my plan. So I now have two clean 8TB drives and the old 4TB with all the data sitting on my desk.

Do I have any options to get the data from the old 4TB and ideally onto the new 8TB mirror drives? Any help is appreciated.

Windows is drag and drop, in Linux use cp

Thanks for the quick response Vegan. My issue is not how to copy data but rather how do I mount the drive. I was told by WD support that I can’t just mount it as a normal drive as it’s configured as a network drive. And I can’t simply take out one of the 8TB in the Mirror, insert it and copy, and then reinstall the 8TB. I’m hoping someone has another option or will tell me WD support was incorrect.

Not sure I 100% agree.

Raid provides a moderate level of protection against failure of the only moving parts in the unit - which has some merit. So if you are diligent, and actually replace a bad drive promptly upon failure… . you do get protection.

So - does raid1 wear drives faster? I challenge that point. If you are mirroring. . .the two drives will wear at roughly the same rate as a single drive. Even if they do wear sooner. . . that is your price for “security”.

Note that Raid1 is PART of a backup strategy. Don’t discount theft, house fire, or ELECTRONICS failure as causes of a NAS failure. Or most likely. . . . a rouge firmware update that bricks the unit.

dsw & NAS - Thanks for the detailed replies. Unfortunately, I won’t be able to try them. When I installed the old (good) 4TB, it now says its bad. I even tried removing both 8TB drives and reinstalling the two 4TB and it says they’re both bad. When Drive 1 went bad, I immediately removed Drive 2 as it was still intact. Now it shows as a bad drive. At least I have cloud storage for the data. I was just trying to restore the local data in case there was some data (old pictures,etc) that never made it to the cloud.

As for RAID vs JBOD, I see both points and personally feel it depends on your usage and needs. In my case, I have Acronis s/w and cloud storage, iCloud & OneDrive as additional backup. My local MyCloud gets backup usage only, so the disk activity isn’t daily and heavy. RAID 1 works well in my situation and if one drive fails I’ll promptly replace it with another 8TB and rebuild.

Again, thanks for all the help and quick responses!

lots of good info here.

I never start changing disks in my NAS system until I have two backups to external USB disks.

take pictures of the set up of your raid setting and how you uses the backup program like “USB Backup”

There is a config options backup but I never trust it.

Now having extra USB backups if raid re set up with larger disks does not work - you can try the restore option on the USB backup app.

and as noted the disks are EXT4 formatted so best NOT to connect to a Windows or Mac OS computers.

and if the power is going to glitch it seems to like doing that while in raid rebuild mode.

part of a NAS system is UPS and a backup.


I use a Raspberry pi for my Linux but Debian is easy to boot on my old Mac system too.

PS - the USB backup disk can be in Windows format.