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Services-specific resource architecture & constraints


 While standardization on the construct of one or more "VM" resource pools for the server resource requirements is necessary and an important step, it is not sufficient. We need to look at the entire solution across a number of dimensions in order to safely and successfully deploy complex solutions onto a virtualized-dominated datacenter world.

However, it would be too complex to introduce solution specific resource definitions for each and every solution that a given customer might deploy. We need to find a workable compromise that allows complex services to benefit from the virtualized and highly automated environment while at the same time ensuring optimal deployment for the solution requirements. After reviewing a number of complex solutions including SharePoint and Exchange, it appears that a number of dimensions have to be expressed and designed into any resource architecture that will host complex services:
  • Hypervisor feature support – a better definition might be shared infrastructure: dynamic memory, high-availability and disaster recovery techniques such as live migration.
  • Placement rules: certain scenarios, such as Microsoft Exchange, require 1:1 deployment between an Exchange server and a physical host. While it is permissible to deploy another workload to the same physical host, placing another Exchange server on the same physical host is not supported. While the product documentation will actually support placing more Exchange servers onto the solution, the recommended deployment strategy – due the nature of the built-in HA/DR architecture of Exchange – is to not deploy more than one Exchange server onto a physical host.
  • Storage architecture: we need to be able to identify the storage type and architecture, e.g. DAS or SAN, for storage-intensive and sensitive workloads such as Exchange or SQL Server. While this requirement obviously goes against the entire ideal of virtualization and standardization, the real world is unfortunately not quite as advanced today.
  • Storage IOPS: We also need to be able to provide the storage-sensitive VM with optimized ways of accessing the storage primarily guaranteeing IOPS. Currently the hyper-v solution does not provide storage QoS which would obviously be an elegant way to ensure the right level of IOPS support for any given workload.
  • Network performance: similarly to storage, complex solutions have very specific requirements on network performance. The good news is that Windows Server 2012 provides ways to manage network performance either through QoS (ideal) or through SR-IOV (high-performance).
  • Run state change management of mixed state environments, very common within existing complex services is especially complex where mixed stateful and stateless settings span across VMs (through roles) and within VMs (through files, registry). This aspect of complex solution management is beyond the scope of the proposal but something to consider: how to leverage IaaS optimizations offers on solutions running states?
With these constraints in mind, there are six categories or types of solution patterns emerging based upon close collaboration between the application workload architects driving the aforementioned PLA’s and the infrastructure architects driving and defining the IaaS PLA: 
  • The Messaging-category: Messaging is a major workload in most enterprises and has a number of constraints and rules when deploying in an IaaS-type environment.
· Hypervisor features: dynamic memory and hypervisor HA/DR features disabled
· Placement: 1:1 Exchange server and physical host deployment, VM's of other application types are OK
· DAS is the preferred storage recommendation because of presumed cost and data segmentation.
· Network QoS required

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