I have a PR2100, OS3, with a single 8TB disk formatted as JOBD. Since the disk is full, I bought a new 20TB disk. We don’t use the NAS non-stop; we turn it on when needed, sometimes only once a month. I was thinking of configuring the new disk in RAID 1. Later, I would buy another refurbished disk for backup. So, the new disk would be in the NAS device, and the additional refurbished disk would be inserted, for example, once a month to store new data on the backup. Then, I would remove the backup disk from the device.
I am wondering how to do this most easily. Is the described order correct? I remove the 8TB disk from the device. Insert the 20TB disk and format it to RAID 1. Turn off the device and insert the existing 8TB disk. Turn on the device and manually transfer all data from the 8TB to the 20TB disk. In the future, I buy a refurbished, e.g., 22TB disk and insert it into the NAS while the device is running. Options for formatting the new disk should appear. Follow the instructions to perform formatting and backup. Then I can remove the refurbished disk from the device. After, for example, 1 month, I reinsert it into the turned-off device. Start it up, and RAID 1 will automatically update the copy. Then remove the refurbished disk from the device and repeat the process approximately every month.
I’m not clear on why you add, then remove a disk every month or so. Raid is not a “backup” strategy.
Nonetheless, the short answer is No, that won’t work.
The longer answer:
You can not create a Raid 1 array with only one disk. You need 2 as they “mirror” each other.
Changing the Raid mode (here from JBOD to Raid1) will require reformatting both drives, building the array and then sync’ing both drive. So you would lose your data on the 8TB.
In Raid 1 mode, drives of different sizes leave you with unusable space for the raid. In your case, your 8 and 20tb drives would result in a mirror of 8tb (the lower capacity). You may be able to create a separate volume with the remainder of the 2nd but this volume is independent (not mirrored) from the others. A mirror of 8TB does nothing to increase capacity, only redundancy (still not a bad thing).
Once a successful Raid 1 is created, you can increase the capacity by swapping out a larger drive for one of the smaller ones. You’d have to wait until they resync, the swap the other drive with a larger one, wait until they resync, then expand the array to the new capacity. Depending on the drive capacity and content, this could take several days to more than a week to complete.
In Raid 1, anytime you pull a drive out, the unit will report a drive failure and you’d be in degraded mode (no more redundancy). You would still be able to access all of your data. Once you insert a new drive, the raid will resync which may takes several days depending on how much data you have.
If your intent is to backup the NAS in case of a failure other than 1 disk drive (Raid 1), I’d suggest getting a large USB drive and plug into the NAS, the use the backup utility to backup the content to the USB. You can set the NAS to power up on a schedule, run the backup jobs, then shut down.
Bear in mind that OS3 is end of life. There is no support from WD. I think this makes having a true backup critical. It can be upgraded to OS5 but the PR2100 is scheduled to go End of Life in Dec 2026. If you upgrade to OS5, you should backup everything before hand in case something goes wrong.
