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The need for Advanced Features within Server Virtualization Part 1

Server virtualization is nowadays commodity. The last years I did not see a customer which is not using server virtualization in some way. Logically step for every organization, but I have seen many customers starting with server virtualization without a real plan or vision. Causing lot of performance issues or implementation of server virtualization infrastructures with lots of features not used or enabled. In some way many customers have chosen to use the most feature full version of the suite, which makes me wonder if all those features are really needed and used.

In this article I will describe the most known features and my opinion it's really needed within the infrastructure. I will use the features available in VMware vSphere, Citrix XenServer and Microsoft Hyper-V.

High Availability (vSphere/XenServer) / Host Clustering (Hyper-V)

High Availability of Host Clustering is a feature that arranged when a hypervisor node (physical machine) fails the current Virtual Machines (VMs) are automatically restarted on one of the other nodes. Because normally a hypervisor node will host several VMs this is a very useful feature. Although the functionality is for a time frame not available for the end user, the system administrators don't have to start all the machines manually. Remember that you also need to have knowledge of Fail Over Clustering when using Hyper-V (this is the technique arranging this features).

Usefully:             4
Necessity:          3

vMotion (vSphere) / XenMotion (XenServer) / Live Migration (Hyper-V)

My personal favorite. With vMotin/XenMotion/Live Migration it is possible to transfer a running VM to another hypervisor used without (minimal) interruption from the end user perspective. Ideal for maintenance on the hypervisor host it selves or for manually arranging the load on the available hypervisors. I think this is the most used features within the server virtualization products.

Usefully:             5
Necessity:          4

vCenter (vSphere)/ XenCenter (XenServer)/ Virtual Machine Manager (Hyper-V)

Management of the hypervisor infrastructure is just like any other big infrastructure crucial. All products offer (a paid) central management suite, which is actual a requirement to maintain an infrastructure with more hypervisors a central management feature is a requirement. A management tools also offers additional features like role access and is for some other features a requirement.

Usefully:             5
Necessity:          5

Distributed Resources Scheduler (vSphere) / Workload Balancing (XenServer)

This feature continuously monitors the hypervisor infrastructure. If a host is getting overwhelmed this feature moves VM or VMs to the other hosts, so the resource usage is spread over all hosts. In theory this sounds perfectly, but in practice I see that this feature is doing nothing (because there is no high load) or the infrastructure is oversized and VMs are continuously moved between the servers (no practical experience with XenServer, I have seen this only on vSphere). However DRS can also be used to host VM's on a specific group of hosts (on vSphere, don't know if XenServer this supports) to arrange dividing for example VDI Desktops and Back-end Server, while arranging that when a host fails the other group of hypervisors can be used.

Remember that some other features are dependent of this feature.

Usefully:             3
Necessity:          2

Resource Pools (vSphere/XenServer)

With Resource Pools a set of resources can be connected to a set of servers. The vision behind is that specific servers can use more resources of the host than servers in another group. However with resource pools the complexity of resource usage/reservations is raised a lot and often causes that resources are not available for a group of servers, while the host has enough resources available. It's a kind of trend not to use resource pools and just let the hypervisor platform divide the resources between VMs available on the host.

Usefully:             2
Necessity:          1

Distributed Power Management (vSphere) / Host Power Management (XenServer)

With Green IT in mind this feature is developed. The feature monitors the usage of the hosts and if resource usage is low one of the hosts will be turned off. Again from a technical point this is wonderful feature, but this is only a benefit for real large infrastructures with tens/hundreds of servers. If there are less hosts I don't think shutting down one or two hosts will really lower the costs into the datacenter. This feature is also dependent of DRS/Workload Balancing.

Usefully:             3
Necessity:          2

Storage vMotion (vSphere)

As far as I know this feature is only offered by VMware currently. With Storage vMotion you can a running VM from one data storage to another. Technically this is a really cool feature, but if you really consider it the feature is only available when placement and/or disk usages of a VM are not taken into account. With a proper planning and good estimating's you would not need this feature, actually.

Usefully:            4
Necessity:          1

To be continued

In a second part I will continue with describing and mentioning my opinion on the feature and give a final conclusion on the necessity of all the features.