For Multiprotocol data, Isilon merges Windows and POSIX permissions and Celerra (VNX) keeps them separate.  If if you execute a robocopy, it will completely erase all POSIX from the file or folder and replace them with the ACL that was on the Celerra platform.   Multiprotocol migrations need to account for that and can be accomplished by a simple process that includes an initial rsync to get UNIX ownership (UID), and symlinks copied on disk, then a robocopy to lay down windows ACLs (which erases the POSIX permissions from the initial rsync), and then a final rsync that will then merge POSIX mode bits into an ACE within the ACL.
After migrating CIFS and NFS data from a VNX/Celerra platform to Isilon I get permissions  denied messages for users, including the owners of the files. Why?
Permissions denied for users in Multiprotocol environment.