I want to create a software linear raid between 2 and eventually more devices

I was wondering if this will work:


Can I mount a disk to a disk folder which already has data without corrupting them ?
If yes is the above mentioned command correct?

I don't think it will work. The mdadm man page mentions "component devices". "/home/george/Dowloads" is not a device.

I tried this:

First of all , let me thank you tommylovell

Secondly since this command doesn't work , is there any way I can add to an existing folder one or more hard drives?

I think you might be faced with shuffling data around a bit.

If you took your /dev/sdb1 partition and created an LVM Logical volume on it; moved your directory contents to it; then mounted that LV at "/home/george/Dowloads", that would do what you want. Then when you wanted to add more space, you could create another physical volume, add that PV to the volume group, and expand the logical volume into that space.

The problem that you'll face here is if that that directory is in use. ('lsof +D /home/george/Dowloads' will tell you, of course.)

If you have LVM, adding the new space to an existing VG gives you a lot of flexibility in moving the data around on those volumes later when you replace drives... (Or if /home is already on an LVM volume now - you didn't say, just adding more space to that LV will solve your problem.)

Doing this type of work generates a lot of anxiety. I would suggest having a good, tested backup.