Ciao to everybody from Italy!
The title I've used could be read as a stupid one. Ok, it could be, but...
I've spent a lot of time to search the web for "what to do if a Software Raided disks (Raid1) have problems"? Meaning that I'm not sure about the actions to be performed for data recovery in case of a disk failure.
In depth, the configuration I would use is:

/dev/sda = 1 TB (or more). /dev/sdb same as sda.
/dev/sda1=12GB with all the stuff needed to work (kernel, boot and so on). This will be the boot disk.
/dev/sda2 (1TB-12GB) as RAID1.
The same RAID configuration will be applied on sdb (1TB-12GB) The first 12GB on sdb1 could be empty or could be a mirrored image of sda1 via "dd" command..

Then what to do if sda1 (or sdb1) goes to hell?
All my data (/dev/md0) are still available or should I kill myself?

A friend suggested to avoid the use of RAID and switch to LVM along with a solid NAS for keep data saved.
ANY answer is really welcome.
Thanks to everybody and forgive my poor english.