Error message in log or on screen:
ERROR : cannot join pool [The hosts in this pool are not homogeneous. reason: Updates on local host xenmaster1 and pool host xenmember2 differ] - abort
If you want to install a new member server in an existing pool and your pool update list file look like:
!XS82ECU1005.iso !XS82ECU1009.iso !XS82ECU1012.iso !pvsaccelerator.iso=1.0.9
the pool join will failed.
Some fixes contain older version of the same fix part but if you install updates not with fsi but XenCenter you have to change the pool.upd file manually.
Add missing updates to pool.upd file: