With vSphere 5.5, Not only removes the 32 GB RAM hard limit on ESXi 5.5 Free version. and also increased the host manageability wth vCenter server Appliance 5.5. You can manage more hosts and virtual machine with vCenter Server Appliance configured with default embedded internal database. VCSA designed to remove the dependency of windows operating system for vCenter server installation.

Below is the snapshot taken from the vSphere 5.1 documentation

It Clears states that with vSphere 5.1, The embedded database is not configured to manage an inventory that contains more than 5 hosts and 50 virtual machines. Exceeding these limits can cause numerous problems, including causing vCenter Server to stop responding.

It was real concern from the administrators that they are not able to manage more than 5 ESXi host with VCSA 5.1 installed with embedded database. It can only support 5 host and 50 Virtual machines. VMware addressed the concern of administrators, Now with the release of vSphere 5.5, vCenter srever Applinace now re-engineered with embedded vPostgres database that can support upto 100 vSphere hosts or 3000 virtula machines.. With new scalability maximums and simplified vCenter Server deployment and management, vCenter Server Appliance offers an attractive alternative to the Windows version of vCenter Server. I believe this post is informative for you and Thanks for Reading !!!!