I hope I'm not completely dead, but hoping someone has a solution-
I have (3) 4 tb disks in bays 1-3 and a 1.5 tb disk in bay 4. I purchased a 10tb to place in bay one, and when that populated i was going to replace bay 4 with the old (actually only a few months old) with the 4tb from bay 1. Well, here's the problem. I pulled out bay one and replaced with the 10tb disk. I was having trouble with the sled as it has a slightly different configuration. to verify i also pulled out bay 2......... Well, once I resolved i placed bay 2 back in and the system now says bay 2 is dead. I then put in all original drives in their respective bays (nothing has been written to these drives), and now it shows as all are dead...... Is there a work around???
If I am reading you right and you pulled two drives of a 4-drive RAID5 with the power still applied, then you are lost. Two of your drives are out of sync with each other and the other two, and you need a minimum of three in sync to have a usable volume.
Netgear paid recovery can probably recover most, if not all, of your data since you didn't write anything to it. You can use that 10TB in a USB dock to hold the recovered data while you do a factory default with the current drives. I assume you wouldn't be asking this if you already had a backup, in which case you just factory default and restore from backup.
I don't understand why you didn't just replace the 1.5 with the 10. End result would be the same with less resync time.
