A blog by Steven Johnston

What has changed in vCenter Server Appliance 5.5 (vCSA)?


Strategically it makes a lot of sense for VMware to decouple themselves from the Windows Server OS for management machines. There are many advantages to doing this which benefit SMB and Enterprises such as simplified install and no Windows or SQL licenses required. These advantages are also valid for Service Providers along with the automation possibilities it brings.

So lets look briefly at the history of vCSA:

In vSphere 5.0 along came vCenter Server Appliance (vCSA). DB support was embedded (DB2 or Postgres) or externally on Oracle. The single biggest problem was that using the embedded database it was severely limited. So much that it was relegated to test labs.

vCSA with vSphere 5.0/5.1 – Supports Max 5 Hosts and 50 virtual machines.

The new version with vSphere 5.5 has the same DB options (with embedded on Postgres) but has removed this embedded DB limitation taking that up to well past what most customers are ever likely to use on a single vCenter

vCSA with vSphere 5.5 – Supports Max 100 Host and 3000 virtual machines.

There are however still other things holding the vCSA back from dominance as the preferred method of vCenter deployment. vCenter matured on the Windows platform and had capabilities built on.

  • Linked Mode (uses Microsoft ADAM)
  • Heartbeat (only works with SQL)

These capabilities are what to this day are still missing from the virtual appliance and are some of the reasons vCSA cannot be used in certain production environments. For the vCSA to get these features means they need to be Linux friendly and that probably means using different methods rather than a port of existing software.

Even for those that can live without Linked Mode and Heartbeat the single biggest reason why people will stick with a Windows vCenter is that Update Manager (VUM) does not come integrated in the vCSA or have a standalone virtual appliance. There is also a 1 to 1 relationship between vCenter and Update manager meaning for every deployment assuming you want to use VUM you will need a Windows Server and a SQL database anyway, so why not use it for vCenter too.

Continuing to deploy vCenter on Windows is probably the route many people will still take as it takes no real extra thought. Components like SSO have made that install more complicated so it makes real sense to want to simplify this and the vCSA is definitely the way to do this.

Until at least the Update Manager component has its Windows dependencies removed, made into a virtual appliance or integrated into vCSA, we will continue to see vCSA reign as the quick and easy pop-up VM in the lab but not in Production. That said, let me not play down what an important milestone this is towards the removal of Windows OS’s in vSphere administration, the core vCenter functionality is now here in vCSA and this is a great win for VMware at this stage. Addressing the VUM component next is likely to swing sufficient number of customers over to using vCSA and it would likely snowball from there.


  1. Great article!!! I have one question and a comment:

    1) In your post you state that in 5.5, that the Embedded DB has been expanded. Do you know what the capacity is (Hosts/Guests)?

    ->According to ‘Mastering vSphere 5.5 (sybex): the number of hosts and guest have been increased, but the embedded DB remains the same size (5 hosts and 500 Guests). Your blog (only a month old) is the only one I have seen (I have read a bunch) that makes this statement regarding the Embedded DB.

    2) You can connect a standard Update Manager install to the vCenter Server Appliance (VCAS). I would suggest you just follow the standard guide. This one is still for vSphere 5.1, but the 5.5 version hasn’t changed much, so it should be pretty straightforward.

    See the Citrix Documentation vSphere Update Manager 5.1 Documentation->Installing Update Manager

    • I am hoping you can provide the DB info as I really would like to deploy the VCSA into our VMware environment 🙂 and if 5.5 has the same limitation as 5.0/1 then I can’t put in in production 🙁

      • Hi Derek,

        Thanks for your comments.

        For your question number 1. See the vSphere 5.5 Configurations Maximum document on page 7 ( That document shows maximums of 100 hosts and 3000 guests with the embedded DB in 5.5.

        On your comment 2. I agree you can do this but since you are using a Windows license and a SQL license to do that, why not just install the Windows version of vCenter on the same machine. The Windows version is still the most feature rich. Saving those MS licenses (the SQL ones in particular) in my opinion is a key driver to moving away. It of course isn’t the only reason why you might want to do this, the installation of an appliance is easier and for Linux/Unix shops the preference would be to steer clear of Windows to mention just a few other reasons.

        There are some other KB’s worth reading before deploying the vCSA.
        This one on Minimum requirements (which actually states the 100/3000 limitations from above as well) –

        This one on what services are bundled is also worth a read. [Edit (thanks Bogd) – You can use PowerCLI by connecting to a VCSA just as you could with a windows based vCenter, what this kb article is stating is that you can’t run powershell locally on the server, makes sense since it isn’t a Windows OS.] It mentions some things I didn’t mention in my article such as if you use PowerShell, with vCSA you won’t be able to do that anymore. For me personally I am a huge PowerShell fan and my preference for scripting with vCenter is with PoSH so this sucks but isn’t a deal breaker as there are other ways to do scripting with vMA I guess.

        I would suggest you both try it out in a lab and read through the VMware KB’s. If you play with it for a while then the limitations that actually affect you will come out and some that you thought may, may not. It isn’t always obvious without trying it out and living with it.

        PS. Sorry for the delayed reply. I have spent the last week moving house, what a nightmare 🙂

  2. One small issue I had to address: you can use Powershell with vCSA just fine.

    The problem is that, since the underlying OS is not Windows anymore, you do not have Powershell available in the OS by default. So you cannot run Powershell directly from (let’s say) an RDP session to the vCenter machine.

    However, you can use any other Windows computer, run Powershell/PowerCLI on it, and connect to the vCSA. That will work perfectly, just as it does with “standard” vCenter.

  3. What is the maximum number of vcenter instances that we can install?

    • Hi Eddy, I am not sure I follow the question. You can install as many vCenter instances as you want. You of course will need to license each one.

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