One of my favorite radio talk hosts talks about the importance of having the “heart of a teacher”. When I started out in IT, I thought I wanted to be in tech support, teach others how to use their computers, and how to make the technology work for them. I have come to realize that while I enjoy helping others, I prefer to talk about concepts, and help them understand storage and virtualization. I am going to spend the next several posts going through some of the VMware storage concepts, in what to many may seem simple terms, but many of the people I talk to do not have a solid understanding, so I think it is always wise to level set, to start from a common point as it were. While there are many blogs out there with some incredibly technical content on this, many well written and helpful, I thought I would give this my own slant in an attempt to help some of the people I interact with and meet new ones. Feedback is appreciated, and I am always open to suggestions for new topics.
VMware in general is all about abstraction. With compute we put the software layer between the physical hardware and the operating system. This enables us to have portable servers, and to consolidate many workloads on to a smaller physical footprint. When we think about this from the storage side of things, it is not so much different. If we think about VMware creating a container to hold many servers, then a datastore, storage presented to VMware to hold Virtual Machines can be considered a container to store the hard drives and configuration files that make up a Virtual Machine. This storage is presented as one or more logical drives, datastores in VMware terms, up to 64TB in size. The reason behind sizing a datastore will be covered later, and is certainly open for discussion, but it is enough to know for now that we create a datastore from logical disk space.
When creating a Virtual Machine, VMware will ask you how much space you want, and which datastore you want to place it on. This will again be covered in a future post about design, but it is important to note, a datastore can contain multiple Virtual Machines, much like a VMware Host, physical machine running VMware, can contain multiple Virtual Machines.
Each VMware Host machine, provided it contains local hard drives, will have a datastore called “Local Datastore” or something similar. This is not a bad thing, it can be useful for Virtual Machines which you do not want to be able to move, but it is limited in that shared storage is required for high availability and resource distribution. With the release of VSAN in vSphere 5.5, as well as many Virtual Storage Appliance, VSA products, this can be used as shared storage as well, but more on that later.
To wrap up, storage is one of the more critical aspects to virtualization success. There are many more features to cover, I will be explaining many of the VMware features as well as where each different HP storage product may make sense as well as some reasons why I personally would choose HP over competitors products. Stay tuned and please let me know if there are other topics I should be covering, or if there is more detail needed.