“I close my eyes, and think of home.
Another city goes by in the night.
Ain’t it funny how it is,
you never miss it ‘til it has gone away.
And my heart is lying there,
and will be ‘til my dying day.”
We would like to dedicate this book
to the greatest band on earth, Iron Maiden.
Introduction to the book
When talking about virtualization and the underlying infrastructure that it runs on, one component that always comes up in conversation is storage. The reason for this is fairly simple: In many environments, storage is a pain point. Although the storage landscape has changed with the introduction of flash technologies that mitigate many of the traditional storage issues, many organizations have not yet adopted these new architectures and are still running into the same challenges.
Storage challenges range from operational effort or complexity to performance problems or even availability constraints. The majority of these problems stem from the same fundamental problem: legacy architecture. The reason is that most storage platform architectures were developed long before virtualization existed, and virtualization changed the way these shared storage platforms were used.
In a way, you could say that virtualization forced the storage industry to look for new ways of building storage systems. Instead of having a single server connect to a single storage device (also known as a logical unit or LUN for short), virtualization typically entails having one (or many) physical server(s) running many virtual machines connecting to one or multiple storage devices. This did not only increase the load on these storage systems, it also changed the workload patterns and increased the total capacity required.
As you can imagine, for most storage administrators, this required a major shift in thinking. What should the size of my LUN be? What are my performance requirements, and how many spindles will that result in? What kind of data services are required on these LUNs, and where will virtual machines be stored? Not only did it require a major shift in thinking, but it also required working in tandem with other IT teams. Whereas in the past server admins and network and storage admins could all live in their own isolated worlds, they now needed to communicate and work together to ensure availability of the platform they were building. Whereas in the past a mistake, such as a misconfiguration or under-provisioning, would only impact a single server, it could now impact many virtual machines.
There was a fundamental shift in how we collectively thought about how to operate and architect IT infrastructures when virtualization was introduced. Now another collective shift is happening all over again. This time it is due to the introduction of software- defined networking and software-defined storage. But let’s not let history repeat itself, and let’s avoid the mistakes we all made when virtualization first arrived. Let’s all have frank and open discussions with our fellow datacenter administrators as we all aim to revolutionize datacenter architecture and operations!
You, the reader
This book is targeted at IT professionals who are involved in the care and feeding of a VMware vSphere environment. Ideally, you have been working with VMware vSphere for some time and perhaps you have attended an authorized course in vSphere, such as the “Install, Configure, and Manage” class. This book is not a starters guide, but there should be enough in the book for administrators and architects of all levels.
For those who prefer to read offline, or use an e-reader. We have made all versions available for free. Download them here. Note that we may update the book in the future, as such we recommend to read the online version, or download a new copy regularly.
- Download vSAN 6.2 Essentials PDF
- Download vSAN 6.2 Essentials EPUB
- Download vSAN 6.2 Essentials MOBI
We decided to give the book away for free. If you enjoy the book we hope you will consider donating to charity. It doesn't matter how small or how big the amount is, all donations help! Two of our suggestions, and non-profits we personally support are, and of course helping them would be appreciated by us:
Duncan supports: Hardcore Help Foundation (A donation of € 10,- will provide clean, safe water to a family for two years.)
Cormac supports: Alzheimer Society of Ireland (A donation of €10 can give an exhausted carer a much deserved break)
Cormac Hogan and Duncan Epping