This week I passed the VCAP-DCD5 exam, but having already passed the VCAP-DCD4 exam I actually found it a little harder than I expected. I can’t tell you any specifics of the exam itself (other than what is on the blueprint) but I would like to share my own study method with you. You will need to be VCP5 before you can take this exam (the limited time period that excludes this pre-requisite is almost up), but even if you have done the VCAP4-DCA/DCD before, you should take a fresh approach to the DCD5. Something that helped me a lot was my ITIL experience, as I’ve previously had key involvement with Capacity and Availability management, in addition to being ITIL v3 Foundation certified . I’ll touch on this in a moment, but bear in mind that this is a Design exam and not a technical exam. Sure there are many technical areas, such as system requirements that you need to be aware of, but you need to have experience at either producing designs for your own organisation, or consultancy at delivering designs for customers. Without this knowledge, you may struggle with some of the questions around best practice, or picking the ‘best’ answer from multiple possible correct answers.
Networking is a critical component of any virtual infrastructure, and often it’s the management networks that are overlooked. Back in the day before virtualisation, management networks were considered less important than production, and it wasn’t too much of a big deal as it only provided console access (E.g. iLO, DRAC), SNMP monitoring, web interfaces, and so on – it just didn’t impact production. I have noticed that this mindset has crept into some vSphere designs where management interfaces lack any form of redundancy. Why is this so important? Well for starters ESXi uses the Management network for vMotion, Fault Tolerance (FT) and HA. In fact if your management interface has no redundancy you’ll get a warning as described in VMware KB 1004700. Without redundancy on your management networks, these features will not work. In addition, you may be faced with mixed ESX and ESXi environments where the management networks are different between ESX/ESXi. Management on ESX uses the Service Console network, but ESXi uses a vmKernel network called Management Network. Duncan Epping of Yellow Bricks has an excellent article on VMware HA here, also check out Frank Denneman and Duncan Epping’s HA and DRS Technical Deepdive book is an excellent read and I recommend this especially if you’re studying for the VCAP-DCA.
I remember when I first started using Microsoft Cluster Servers with SQL 2000 and Exchange 2003, and I had plenty of experiences (good and bad) especially once when I lost the quorum disk and I was due to go on holiday the next day! When I saw this topic on the VCAP-DCA blueprint I thought ‘oh’. Funnily enough, whilst I have had plenty of experience with physical clusters, I’ve never had to implement clustering in a vSphere environment. Due to certain complexities of MSCS you can achieve unwanted downtime (such as when I lost the quorum disk, or through mis-configuration) and can be a headache in itself. I’m not sure to what level the VCAP-DCA exam will require us to configure MSCS, but I am confident that it’s just configure the vSphere environment and not the other things you would normally have to do (SAN zoning, shared quorum disk, etc).
The first and only document I will use for this section on MSCS is Setup for Failover Clustering and Microsoft Cluster Service, and it’s only 36 pages so don’t worry you won’t be spending the next three weeks on MSCS alone! In fact, the VCAP-DCA blueprint lists each section in order on this document so it’s a safe bet!