Hi,  The “recycle disks" disks option is grayed out because, the disks might consist of shares/luns which needs to be removed before you recycle the disk. Hence please cross verify if the disk which needs to be removed is currenlty not being used. (all the file system. luns and checkpoints needs to be removed for recycling disk).  If you are sure the disk is free than I suggest you to please open a service request with EMC support for them to look  into the issue.  Regards Shivanand
Is there an option in Unisphere (or somewhere else) to remove a couple of disks from an existing pool and resize the pool? I want to buy some larger disks and create a new pool but also keep the old pool.   I see the option in Unisphere, under pools, under disks, to “recycle disks” - but it is grayed out.  I have admin access to Unisphere and there is enough free space in the pool to remove these disks. 
Removing Disks from a Pool on a VNXe3100