If I have disks in a RAID-1 array, can I take one of them out and plug it into a different system to be read?
This means, on the target system, treating the disk from the RAID array just like an ordinary disk, regardless of any controller/driver support and without doing any rebuilding.
The idea is that if my array (of 2 disks) degrades, I can plug it into a different system and don't have to get another disk of the same capacity (which gets harder as time passes) and (hopefully) even without access to the original system, in the event that the controller or motherboard goes bad instead of one of the disks.
Best Answer
Disregarding RAID implementation? Then the answer should generally be no: you can not assume that all hardware controllers treat disks in such a transparent way.
However, in the case of software raid in Linux (md+raid1) then yes, there's no disk header or secret block-level optimization going on there.
In the case of Disk Mirroring in Windows, it involves the disk having been initialized as "Dynamic" and, well, should just work, given that the system that reads it can understand the dynamic volumes - in other word it will most likely only be accessible from another system running Windows.
In the end; you can try connecting the disk regardless of controller. If it works, it works. No controller will damage the data on the disk as long as you don't tell it to - i.e. as long as you don't execute an operation such as "initialize" or anything.