xquadv

Hi, I have DSM 5 with update 7 running. All together i have 5 3TB disks where one of them resides within a 3,5" expansion in the 3,5" slot of the HP NL54 microserver. I have problems with that expansion, as the disk regulary can't be initialized (disk is ok), so I'd like to remove this disk of my raid 5. Is there an easy way to remove this disk of the raid to fail back to a 4 disk raid? I know that I can do it on the command line with mdadm but I don't know how DSM reacts on it. Any help's appreciated. Thanks.