I need somehow to figure out the disk with the badblocks. I could leave in: 

/dev/sda 320 gb
/dev/sdb 320 gb
/dev/sdc 1500 gb
/dev/sdd 1500 gb

and leave this disk detached: 

/dev/sde 1000gb

See then if clicking sounds continue (they should as I believe it is one of 320gb disks)

Then document everything: 
Start by checking the raid status: 
cat /proc/mdstat

in more detail: 
sudo mdadm --query --detail /dev/md* (I have md0, md1 and md2)

See devices and partitions (and document here): 
sudo fdisk -l

See volumegroups (and document here): 

sudo vgscan
sudo vgdisplay
sudo lvs

Lastly, try to figure out which one of the actual hardware devices is /dev/sda, sdb etc. One you know those, dymo them.