WD10EARS not working in NV+

Not all 1TB drives are equal in size, even if the same make and model. I have 10 Seagate ST1000528AS purchased in 3 blocks. Originally 8 were in service in two NVX units and two were spares. I have lot three of them, two of which have been RMA's and replacements received. While I have replaced 4 of these from NVX service (2 ea in both units replaced by 3TB drives) two were in service in a third NAS. I had one throwing increasing errors in one of the NVX units, and I thought no big deal, I have plenty of spares. The first two I tried were rejected giving me the same message that you got, although had recently been in service without errors. They had both been connected to a PC and had the partitions removed. I dug a third one out of the cabinet (a refurbished drive in replacement of a failed drive) and it was accepted and resynched.

Although this was the first time I had gotten this error on this particular batch of drives, it is not the first time I have gotten the message on supposedly identical drives. I bought two identical Samsung 500GB drives to expand my old NV+ from two Seagate 500GB drives when I needed more space. The first of the Samsungs was accepted and the volume expanded normally. However, when I attempted to add the second Samsung of the same model as the one that was just accepted, it was rejected, giving me that same message. I wound up using a 750GB drive to expand the volume.

All it take is for a drive to be a single sector smaller than the previously smallest drive and the drive you are attempting to add will be rejected as too small. The only way to know for sure if the drive is too small rather than non-compatible is to back up your data (you wanted a current and complete backup anyway, right?) and then perform a factory default which will wipe all the drives and re-establish the volume. Then you would restore the data from the backup.

One other thing you can try without harming your volume is to backup up your data (Murphy is always lurking) and then shut down the NV+. Remove the three good drives noting the bay each was in. Then install the new WD10EARS as a solo drive and reboot the NV+. This will only take about 15 minutes to format the drive and copy the OS onto it and boot. If it succeeds, then you know the drive is accepted and that it may in fact be slightly smaller than the other three drives or at least smaller than the smallest of the three.