So i decided to stop the parity check - reading in another forum that even if the drive is not readable running a parity check wont solve an invalid or missing drive.
So i stopped the array and ran it it maintenance mode clicked on drive 4 and ran the XFS check.. It found a few errors so i took off the -n and ran it again. Stated to remount the drive and check it if its not there then to go back to maintenance mode and use the -L option. Did that and started the array again as normal and hey presto the drive and all files are back.
It moved some files over to a lost and found directory. They were only a few jpg files nothing important.
I've decided to run the check on drives 1 and 3 as Trurl noted to check connections. Which i also did before i ran the maintenance mode stuff.
I will re run the parity check and make sure that's all in sync too.
Thank you Happy i solved something by myself for once
