The other day we received this question from a customer via Twitter:

@VMwareCares planning to upgrade to 5.1 from 5.0 vcenter. What’s recommended physical or appliance? Ups and downs side of each?

We thought a few more of you might have the same questions so we decided we would take the opportunity to explain the differences between vCenter server and vCenter appliance and under what situation which one should be opted for, over the other.

The vCenter Server Appliance (vCSA) is a preconfigured Linux-based virtual machine optimized for running vCenter Server and associated services. Versions 5.0.1 and 5.1 of the vCSA uses PostgreSQL for the embedded database instead of IBM DB2, which was used in vCenter Server Appliance 5.0 The vCSA embedded postSQL DB supports 5 hosts / 50 virtual machines, with an Oracle DB the vCSA can support 1000 hosts and 10,000 vms. If you configure your vCSA to use an external instance of Single Sign On (SSO), the external SSO instance must be hosted on another vCenter Server Appliance; it cannot be hosted on a Windows machine.

vCenter Server can be installed on a windows Guest OS and can be connected to Oracle or Microsoft SQL. SSO can be installed on the same Guest OS or can be on a different machine. It should be noted that patching of of the vCenter Appliance is not supported.

Below is a table listing more of the differences between the products.

Features vCenter Server vCenter Server Appliance
Guest OS Any Supported Guest OS Preconfigured Linux-based virtual machine (64-bit SUSE Linux Enterprise Server 11)
Database Supported Versions SQL Server and Oracle. PostgreSQL (built-in ) can have 5 hosts and 50 Virtual Machines.Supported External Oracle database.
System Requirement 2 vCPU and 4 GB RAM 2 vCPU and 4 GB RAM
Platform Physical or virtual machine Virtual Appliance
Installation Using binary provided in .zip or .ISO Deploying OVF
Update Manager Can be installed on same vCenter Server or on separate Guest OS. Separate install
Single Sign On (SSO) Can be installed on same vCenter Server or separate Guest OS. Pre-installed.
Networking IPv6 and IPv4 Support IPv4 Support
Linked Mode Supported Not Supported
SRM (Site Recovery Manager) Compatible with SRM Compatible with SRM
vSphere Web Client Can be installed on same vCenter server or separate machine. Pre-Installed.
Syslog Server Can be installed on vCenter Server or separate server and configured using plug-in. Pre-installed and does not have plug-in.
ESXi Dump collector Can be installed on vCenter Server or on a separate Guest OS. Pre-installed and does not have plug-in.
Multi-site SSO Supported Not Supported. Basic SSO only.
VSA (vSphere Storage Appliance Supported Not Supported
VMware View Supported Not Supported