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Like many other administrators, I started with vCenter Server for Windows. So, you can imagine my disappointment when I learned that VMware will deprecate vCenter Server for Windows with the next release of vSphere and instead move ahead with vCenter Server Appliance. According to VMware, vCenter Server Appliance is superior to vCenter Server for Windows in every way and will save customers money by eliminating the need for a Windows license. This sounds nice in theory, but the reality of deprecating vCenter Server for Windows is a little more complicated.
The move from a Windows platform to a Linux platform means you no longer have a ready-made Active Directory (AD) client. Although vCSA has the ability to connect to any directory service through the use of Lightweight Directory Access Protocol (LDAP), its usefulness is questionable. LDAP is an open standard that allows Linux and other non-Microsoft clients to make use of directory services. The problem with this is that it's often unstable or simply doesn't work. Microsoft supports LDAP but doesn't put much effort into improving it because easy access to Linux servers that take advantage of AD detracts from Microsoft's server install base. Because of this, many vCenter installations are configured with local accounts rather than AD, which can result in nonexpiring passwords or limited password policies; this is a serious issue because vCenter Server accounts for your entire data center. It's possible to add security controls to vCSA as a safeguard, but realistically, few administrators will actually do so.
Another issue with moving from a Windows install to Linux is support. Many administrators are already familiar with Windows, and outside of Windows 8, most versions of Windows are similar, with the exception of a few updates and features. This means that, when something breaks, you can use the skills and tools you've acquired over the years to address the issue and get back up and running. A Linux install requires an entirely different troubleshooting process and uses different commands than a Windows install. Inexperience with this troubleshooting process and these commands can lead to mistakes, which can easily make even a veteran admin look like a rookie. Proper training can eliminate this problem, but it'll come at a cost. VMware technical support can help alleviate this problem, but if your administrators can't manage basic troubleshooting on critical infrastructure, you're at a serious disadvantage.
You also need to consider the limitations of vCenter's internal database. This database stores all of vCenter's data, settings, VMs and more. If you have thousands of VMs on your vCenter, the internal database will slow down and could even reach its limit. To resolve this issue, you must add either another vCenter or another database. If you choose the latter, you have a couple options. The embedded database has grown in capacity in terms of the number of VMs and hosts it can support, and you still have the option to use an external database. Windows gives you the option to use SQL, which is a reasonable cost alternative compared to the Oracle option that vCSA provides. The other key consideration behind database selection is where it will run. While SQL is supported in any virtual environment, Oracle only supports its database product on virtual servers that use the Oracle hypervisor. It doesn't make much sense to stand up a different hypervisor for just one database or hardware, so it's better to use an embedded database in which you can set limits.
VCenter Server for Windows can operate on either virtual or physical hardware. By comparison, vCSA can only run on virtual hardware. Although the virtual platform comes with benefits, such as Distributed Resource Scheduler and High Availability, it often sits in the same hardware cluster as production VMs. This means your central management tool is "trapped" in the same environment it manages. To avoid this, you need to create a separate management cluster specifically for your management tools. This is a relatively easy process; it requires additional hardware and licensing resources.
Although vCSA is easy to deploy and comes with a number of benefits, it also has some serious drawbacks that VMware has yet to address. If VMware fails to address these issues, administrators might find themselves longing for the days of vCenter Server for Windows long after its retirement date.
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