Ok, so you are interested in server virtualization technology but you’re wondering what the components of virtualization technology are–how it physically can be put together. Is it different from just a standard physical server? Well yes and no.
You still use a similar server type of hardware but will split up some of the basic hardware components to share the resources. The primary shared hardware virtualization components you need to review are CPU, memory, storage, and network connectivity. Remember, you are now going to focus more around using shared resources rather than a single server environment. This will be explained little more in detail below with a simple example. Keep in mind this is just an example and your virtualization needs may be different from what is addressed here.
Virtual Host Server
The virtual host server is probably the most similar to a typical single physical server. But in the virtual world, you need to provide two main functions, CPU and memory hosting for the virtual guest servers. For the CPUs you want to consider using more cores vs. higher clock speeds. This would be due to the ability of spreading the amount of cores out to the virtual guests. The more cores you have, then the more virtual guest servers you can support. Most virtual guest servers stand idle and are only using the CPUs when a task is assigned to them. Taking the idle averages of all the guest servers will provide you with a calculated number of how many guest systems that can be supported on that one virtual host server.
When it comes to RAM, you want to consider two basic decision points. Total quantity and speed. Some virtual guest servers will require a fixed amount of RAM and use all of it. Others are more dynamic and can map the memory accordingly to the needs of that guest. Bottom line, always lean on more is better.
Storage
Now this were things get a little different from a standard server environment. In order to utilize some of the great features of fail-over and high availability within the server virtualization technology environment then you need to consider a Storage Area Network (SAN) or Network Attached Storage (NAS) device. This storage device will be storing all the virtual guest images while the host servers will be accessing the data. There are many different types of SAN and NAS technologies out there, so you will need to do your homework on what works best for your environment. Typical rule of thumb is that if you have some virtual guest servers with heavy I/O needs (typically database servers) then speed and performance of the SAN or NAS will be a deciding factor.
The other deciding factors for the SAN or NAS are the failover features. Think about it, if your storage fails then your virtual environment just went completely down. Which in most cases could be a number of virtual guest servers no longer operating and no one is able to work. So consider options for dual power supplies and storage controllers. Consider your RAID level to meet your I/O needs and provide optimal performance (i.e. RAID 10 or RAID 50). In some cases you can even build a complete fail-over storage device so if storage device A failed, then storage device B can be activated to support the virtual network environment.
Networking
There are generally two sides of the networking connectivity that needs to be implemented. The side that is most familiar to everyone would be the Local Area Network (LAN), which is basically connected from the virtual host servers to the rest of the network environment. This would be where the office workstations etc. access the network environment. In general you want to have a few network ports assigned to the LAN.
The other main component is the connectivity to the SAN or NAS. This provides connection for the hosts to access storage devices and is not connected to any other networks. In some SAN scenarios you can connect via fiber network cards and fiber switches. In others it’s connected via standard network cabling but uses a protocol called iSCSI. In the past, fiber has provided the optimal speed and performance for storage connectivity but has been the most costly. iSCSI has come a long way in the recent years, has become a business industry standard, and it’s generally not as costly as fiber.
The diagram below provides a graphical iSCSI connection example:
In conclusion the details listed above provide a general overview of what is needed for the hardware components of virtual environment. Every company has different business needs so this will drive your hardware and software virtual infrastructure build out plan. This information should at least provide you with an understanding what is involved and the framework to get you started on your very own server virtualization technology project.
