ZFS can be mounted in 3 case modes - case-sensitive, case-insensitive and mixed.
When backing up from Linux servers(case-sensitive file system), make sure that the casesensitivity for the destination ZFS is also set to case-sensitive.
Please visit the following link for more information regarding the casesensitivity property on ZFS: https://docs.oracle.com/cd/E19120-01/open.solaris/817-2271/gftgr/index.html