My laptop’s HDD is failing, it shows a bunch of signs such as slow file manipulation and clicking sounds. The Linux btrfs partition keeps going into read-only mode to prevent further damage, makes sense, but the windows partition is working fine (for now).
Shouldn’t harddrive failure be evident on all partitions?
It depends on the exact nature of the failure. Controller errors are usually a complete failure. Media failure (magnetic spots on the disk or failed cells in ssd) are often sporadic and only impact data stored in those spots.
Regardless, drives rarely give you any warning. Look at any warning as a gift and get everything off and replace it ASAP.
Yup. I would try to stop using it if at all possible. As soon as you can, dump a full disk image to some other storage. Tools like ddrescue can be useful as they will try to re-read failed sectors to get a more complete image.
Once you have the data (or at least as much is available) to a reliable medium then you can start sorting through it and discarding or saving individual bits.