WD 6TD Thunderbolt Raid 1

So, I havent recieved this yet, but ordered it and then stumpled across a bunch of negative reviews, so looking for some clearity here:

 I want to back up 1 drive with the other, so escentially ill have a 3TB drive, backed up. (going to use it for TimeMachine + Stock Footage Library. 

I hear, that if 1 drive fails, it takes DAYS for the other drive to rewrite the failed drive, in which time, your computer has to stay connected. 

I also hear, that if the Raid Enclosing fails / breaks, all is lost, noway to recover your data, is this true? if so i might need to cancel my order quickly. 



This drive gives you the ability to mirror the data as soon as is transferred to the drive.

No need to setup a backup, just set RAID 1 or 5

I’ve beening using the 4TB thunderbolt Duo in RAID 1 for a little over a month now, i haven’t had to rebuld a drive yet, hopefully will never really have to as i’ve heard good things about the Green dive being much more reliable and ecnomical. My only gripe so far is the speeds. I was getting a good 100ish MB/s read and write in RAID 1 initially but now its gotten terribly slow and sluggish to the point of 40MB/s read and somehow 70MB/s write so just that mere fact alone i think something is wrong with my particular case/drive/system. 

I have read myself about the days it takes to rebuild the drive but i don’t know how it can 2-3 days hopefully doesn’t take that long but you can never be certain untill you’ve done it. You do in fact have to keep the drive conneced to a computer while thee rebuid is in place,