Data Backup

Advice please folks...

A couple of years ago I bought a NAS drive, 2 bay plus 2 3TB discs. I arranged it as a JBOD setup and mapped each disc a drive letter. Drive L acts for the files and drive M acts as a backup.

I have now used up all the space, so I was going to buy a 6TB USB drive as my backup and use both discs in the NAS drive to act as a single drive. That way I can get 6TB of space for files.

My question is, can I delete the data on my M drive and then combine both NAS discs into a single drive letter without having to delete the data and copy it back again. I want to combine the 2 nas discs into a single drive with 6 TB capacity and assign it a single drive letter. Id rather not delete everything, change the RAID setup and copy it back again as it takes ages to copy the files over.

Thanks in advance.

It would depend on your NAS software and its ability to add drives to a volume group. Personally I'd backup to the external drive and rebuild the 2bay NAS and do a copy. If the external drive is USB3 and your NAS has a reasonable controller you should be able to complete the copy in a day or so.

I've been in a similar situation, after a lot of digging about, comparing software raid utilities, etc, the best route was (as others have said)
1) Back up separately to a local drive
2) Back up to a cloud service (I already use Crashplan to backup my NAS)
3) Switched to UnRaid