In today's IT infrastructure when Virtualization is the hot topic, more and more organisations large and small are looking to investigate the pro's and con's of Virtualization.
Virtualization technology has been around for years in one form or another and has improved significantly in what it offers the consumer. But is it necessary? Should you be doing it?
What I will try to do here is provide you with a rundown of the pro's and con's of server Virtualization.
Let's start off with the con's because I always like to end on a positive note :)
Virtualization Technologies
There are a number of different vendors providing hypervisor type technology, the major players being Citrix, VMWare and Microsoft. It can often be difficult to identify the differences between each product and why it is better than the other. It can also be costly to move from one technology to another if you have already invested. Whilst your network can consist of a number of different vendor technologies it is often not cost effective to maintain them so choosing the right vendor and sticking to them is essential. On a plus side, the entry level hypervisors from most vendors are free allowing you to try the technologies out before you invest.
Storage
iSCSI, FC, DAS, NAS; all acronyms associated with storage (yes there are many more) but which type of storage do you choose? Or do you use a mixture of them all? Again depending on which expert you talk to, different technologies will be recommended. In reality, they are all have their plusses and minuses and to a large extent, depends on what you will be running on them. If you have a cluster of highly available virtual hosts then you will probably be looking at some sort of Network Attached Storage (NAS), which can be very costly.
Staff Training
You may have already invested in your IT Staff or you may hire consultant services, either way an investment in Virtualization technology could well mean further investment in either your own staff or 3rd party support. If you plan to virtualize, you will need to ensure that someone is able to support your configuration.
Software Support
Many software vendors may tell you that their software is not supported in a virtual environment - this is happening less these days but it does still happen. It will more than likely work because the OS is exactly the same. What happens if something goes wrong with this software? Who carries the can?
All eggs in one basket
I must admit that it took me a while to let go of the stacks of physical servers in my data centres and take a hold of Virtualization. And I am willing to bet I am not the only one. A lot of IT Managers/IT Consultants don't like the idea of a single server (or small cluster) running their entire network. What if it fails? How do you bring it back online? At least if you have physical servers and one of them fails the rest are still working. This is where high availability comes in and the cost associated with it.
Cost
To get all the benefits and a highly available network and staff/consultants that can support it along with all the required hardware and storage can be very expensive. It is also a minefield choosing the right vendor. If you are running multiple Virtual Servers you will also need to invest in further licenses for those servers.
Now let's look at the Pro's and there are just as many of those as there are Con's.
Energy Cost Savings
Most CEO's these days have Green ICT somewhere on the agenda, normally near the top. Not just because they want to reduce their carbon footprint but because they want to save on the ever rising energy costs. Virtualization means we don't need as many physical servers. This by itself means less electricity used. As a by-product of having fewer servers, they produce less heat, which means less air-conditioning - another energy cost saving.
Reduced Maintenance Costs
By having fewer physical servers we also reduce the amount of physical space they require and benefit from reduced cost maintenance agreements (most Tier 1 Server vendors charge for their extended warranty based on physical machines). We will also need less air-conditioning units and this will require less servicing as it won't be used as heavily.
Shared Resources
Whilst cost of shared storage(SAN) is high, it could also be argued that you are investing in this only once and you will share it with all your servers. This is also true of other hardware, CPU & RAM for example. You buy a single server with 48GB of RAM and 2 Quad Core Xeon CPU's and with the right technology, the software will manage these resources for you and distribute them as needed, making sure the virtual servers you have are getting the resources they need when they need them and giving them back to the pool when they don't.
Flexibility
Virtualization provides us with the flexibility to separate our server roles without investing in more physical servers. Whereas if there was not a physical server to install our newly found SQL database application it would end up on another server that wasn't doing much. With virtualization we can quickly deploy a new virtual server and install our application here (as a side note - this could also be a disadvantage as we could end up with a single server running many different Virtual Servers unnecessarily).
Virtualization is suitable for all sorts of business sizes. Even a small business with a single physical server running Small Business Server is a candidate. What if you want to run a piece of client/server software that will not run on Small Business Server? Segregating server roles can be an advantage no matter what the size of your infrastructure.
There are many other pro's and con's to Virtualization mainly based around the technologies themselves. Hopefully you have gained some insight here as to what to look for if you are thinking about virtualization.
Thanks & Regards,
"Remember Me When You Raise Your Hand For Dua"
Raheel Ahmed Khan
System Engineer
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