Yeah, I learned already that raid is no backup. I heard of companies going out of business because their stupid admins thought raid means everything is safe and sound.
Some years ago, I think I still used freenas 7 two drives died almost at the same time. But I was quite lucky. First, only one drive was completly dead, the other one had a lot of bad sectors. I did not recognize I had two faulty drives in the first place, so I replaced one and the system was resilvering. Freenas told me exactly which files it could not recover. Luckyly I had a backup for all of them. I recopied them and then I found out about the second drive which also explained why freenas could not recover some files. I replaced the second one and everything was o.k. again. But this was a close call. Therefore I try to have a current backup and keep it in another room in case of a fire.
The western digital green drives were a hell in a handbasket. The missing TLER made the situation above a lot worse. The faulty drives slowed the raidz and the whole system dramatically, because they constantly tried their stupid recovery procedure. I have now the red series and I seriously hope that if a drive fails I won't experience those slowdows again.
I still got the green drives I wanted to use them for backup, but I'm still not sure how to do it properly. I got 8 hot plug slots in my 4hu case. If I use 5 for raidz2 I still got three remaining. I want to put them in, do the backup and remove them. Because of their green nature I don't think it's a good idea to built a raid, especially with only three slots remaining. I think I will use them as three single zfs drives.
Is there a way to do the following in freenas:
1. /mnt/Mypool/Mydataset1/Path1toCopy -> /mnt/BackupDrive1
2. /mnt/Mypool/Mydataset1/Path2toCopy -> /mnt/BackupDrive2
3. /mnt/Mypool/Mydataset2/PathtoCopy -> /mnt/BackupDrive3