Is there a hard stop at 50 VMs and 5 hosts or is that just the recommended max?
Embedded database sized to support onlu 5 host and 50 VM's. In case if you wish to have more host and VM's then you have to choose an external database and as of now
From vSphere Document
Important
#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.
Will going to vCenter Appliance 5.1 gain us anything?
benefits with new features of vSphere 5.1
On vCenter 5.0 and 5.1, can you use SQL 2005 or is SQL 2008/2012 required?
Assuming you are asking for Windows based vCenter , below or the DB supported
- IBM DB2 9.5
- IBM DB2 9.7
- SQL Server 2005 64-bit Standard, Enterprise SP4
- SQL Server 2005 32-bit Standard, Enterprise SP4
- SQL Server 2008 64-bit Express R2
- SQL Server 2008 32-bit Standard, Enterprise R2
- SQL Server 2008 64-bit Standard, Enterprise R2
- SQL Server 2008 32-bit Standard, Enterprise SP2
- SQL Server 2008 64-bit Standard, Enterprise SP2
- Oracle 10g 32-bit Standard, Enterprise, One R2 (supported with version 10.2.0.3.0 or higher)
- Oracle 10g 64-bit Standard, Enterprise, One R2 (requires version 10.2.0.4)
- Oracle 11g 32-bit Standard, Enterprise, One R1
- Oracle 11g 64-bit Standard, Enterprise, One R1
- Oracle 11g 32-bit Standard, Enterprise, One R2
- Oracle 11g 64-bit Standard, Enterprise, One R2