Replacing 2 Drives

Without risking more damage by turning the NAS on to read word-for-word the details of what is wrong with the drives, i will recall what the log said - the drives were marked as "dead". When i looked in the log section of the admin console, drive 3 and 4 said the bad sectors were increased by 12 from the last count. So it sounds like bad sectors and in fact, when i clone drive 4, it reports bad blocks.

It started with a power outage that lasted longer than the battery on the UPS. After that, i could get to the data and drive 4 was marked as "dead" with bad sector errors in the log. Before i got the replacement 3TB drive, the NAS reported drive 2 was dead and if i hovered my mouse over the "volume" label of the admin console, it reported "drive is on life support. The following part i am recalling from memory so may not be worded right; Power off the NAS, reinsert the drives and power back on to see if this fixes the issue". It did but only for a short period of time. I could still get to the data. I got a replacement drive, when i looked at the NAS, it now said drive 3 and 4 are "dead" with the same bad sector errors for both drives. It also reported life support again so i turned off the NAS. Removed drive 4 and installed replacement drive. Turned the NAS on and now no volume seen. I turned off the NAS and strated to clone disk 4 to the new disk (which is still running).

I have worked in sysadmin for over 20 years. During that 20 years, i have worked on PC's (break/fix), designed networks and installed networks from the ground up, designed wireless networks, built branded servers (from hardware to software, linux and windows), administration of juniper, cisco, sonicwall etc routers and for the last 8 years run a computer business. So while i do have more than enough experience with many IT aspects, including RAID config's, i have dealt little with X-RAID2 and ReadyNAS devices. Hence my question on a forum where you are encouraged to go for help!