Symantec Storage Foundation and High Availability Solutions gets installed in secure mode by default. You are advised to install SFHA Solutions in secure mode to be able to control guest user access to secure clusters and encrypt communication between SFHA Solutions components. You can choose the non-secure mode during installation; however, the product installer warns you during the installation with the following message:

Symantec recommends that you install the cluster 
in secure mode. This ensures that communication between 
cluster components is encrypted and cluster information 
is visible to specified users only.

The upgrade from non-secure mode continues to happen in non-secure mode. The upgrade from secure mode advises you to control user access to secure clusters.