Virtualization Models

Virtualization technologies can be hold under three types:

Type 1 Virtualization: This type of Virtualization is latest technology at Virtualization and at this model all systems are managed at a virtulization stack. Hypervisor systems are also part of this model. Mainly this model, works as a layer between hardware and guest os.

Type 2 Virtualization: This model needs a operating system installation and a working vmm over this operating system. One common problem is when there is a maintenance issue happens on the os, every guest should be restarted. Typical examples for this virtualization are Java Virtual Machine and .Net Common Language Runtime.

Hybrid Virtualization: This model works as all guest systems talk with the vmm and host os. This is also known as traditional virtualization. Some samples are Virtual PC and Virtual Server.

Virtualization for Green IT

One of the most dangerous affect of a datacenter is energy usage and unfortunately exhaust of hot air. When design our systems we do not even think how to save energy. We are just focusing to finish project. Nowadays, we are discussing energy savings for two reasons: Global economic crisis and saving the world.
As we just add a server for any application we are just talking about adding maybe hundreds of servers. When you think of the functioning times of these servers you will realize that some of your servers are working quite hard as some of them are resting. What we really get is, we use our cpus less than %20 and this causes purchasing lots of full computers. Instead we can use one hardware and share this hardware among the others. At this point, we have the chance of working on one hardware multiple servers and use same hardware utilized 24 hours.
Virtualization takes active role when we try use same hardware for multiple servers. Main function of virtualization is downsizing the energy costs, downtimes and time to deploy new servers. We will discuss virtualization technologies in detail.

Common and inter-system ground noises

In this entry we will talk about ground noises. First of all, what is ground? As a simple way to tell it is the 3rd line when you have a single-phase wiring. 2 lines are connected to your electricity system(ups, generator or city lines) Ok, then why are we connecting a 3rd line? As an unwanted situation, there is a disturbance between the power neutral(generally, blue or white wire) and the gorunding conductor(should be green). These disturbances exist as a result of noise injection into the neutral or grounding wires, wiring faults or overloaded power circuits. One common mistake is while your electrician cabling your system, he can use inappropriate neutral cable size. This also leads to electricity flow to return from ground.
However, Inter-system ground noise is different than common ground noise. Assume that you have two ups systems. First group is grounded by your IT team and the second system is grounded by your building system. When there is a difference in the ground noise between these systems, computers are impacted when they are connected to these different systems. It is also possible to pass noise from high ground noise to lower one with data cables. This situation is known as inter-connect ground noises.
The best way to stop these, all systems should be connected one ground system and connected systems will also have no problem within one ground loop. Additional systems grounding should be added as a tree structure.

Cooling Basics

As a datacenter or computer room owner you should check your expenses about your cooling requirements. On your computers whitepapers, every system has how much electricity uses. So be sure to check your total electricity expenses.
Once you find your total expense in kWatts, you should need to add computer rooms cooling requirements. As a best practice, you can add 400 btu per metresquare area in a average of 3,5 m. height. Ok?
Let's find your total requirement. Multiply your electricity requirement in kWatts for your servers by 3414 and add area multiplied by 400. This number will give you the exact BTU requirement.
As a best practice 59 kWatts cooling capacity system has an expense of 17 kWatts cooling and 5 kWatts for humidity organization. So for finding total electricity expense with cooling, you can assume that for each 59 kWatts server electricity expense you should add 22 kWatts cooling expense if you use CRAC.
We will talk about alternative ways to decrease cooling bills. Headlines will be:
- Hot air/Cold air aisle
- Usage of free cooling systems
- Exhausting hot air as it gets out of the systems
- Usage fresh air from outside if it is tempreature is less than inside
- Having underfloor airflow barriers
Coming soon...

Size does matter in cooling systems

Datacenters which are designed before 2001 has a huge cooling budget. Main reason for such a payment is design of the racks, cooling way and old energy killer systems.
When you design the layout of your cabinets, you should take care of which way your cabinets are facing and where they hot air exhausts.
Generally all rows of cabinets looking one way has the problem of taking hot air inside. This happens because first rows exhausted hot air gets into second rows fresh air intake. For example, when you have ten rows of cabinets there is a remarkable change in the tempreature of last rows.
We will discuss these details in detail in the next posts.

Datacenter Design Fundamentals

In this series of articles i want to write how to make efficient use of power, rack space and expenditures when desigining your datacenter..
First of all, having a datacenter is an expensive task and when you use your resources inefficiently, you also will lose extra money. That is where a good designer take action and make things go better.
As a matter of fact, a good datacenter should be built with three facts; Performance, stability and scalibility. While building a datacenter on these facts also security is a feature that should never be forget.