The following sections provide definitions of the reference workload used to size and implement the VSPEX architectures. The sections include instructions on how to correlate those reference workloads to customer workloads, and how that may change the end delivery from the server and network perspective.
Profile
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Modify the storage definition by adding drives for greater capacity and performance, and by adding features such as FAST Cache and FAST VP. The disk layouts provide support for the appropriate number of virtual machines at the defined performance level and for typical operations such as snapshots. Decreasing the number of recommended drives or stepping down an array type can result in lower IOPS per virtual machine, and a reduced user experience caused by higher response times.
Reference workload
When you move an existing server to a virtual infrastructure, you can gain efficiency by right-sizing the virtual hardware resources assigned to that system.
Each VSPEX Proven Infrastructure balances the storage, network, and compute resources needed for a set number of virtual machines, as validated by EMC. In practice, each virtual machine has its own requirements that rarely fit a pre-defined idea of a virtual machine. In any discussion about virtual infrastructures, first define a reference workload. Not all servers perform the same tasks, and it is impractical to build a reference that considers every possible combination of workload
characteristics.
To simplify the discussion, this section presents a representative customer reference workload. By comparing your actual customer usage to this reference workload, you can determine which reference architecture to choose.
For the VSPEX solutions, the reference workload is a single virtual machine. Table 10 lists the characteristics of this virtual machine.
Table 10. Virtual machine characteristics
Characteristic Value
Virtual machine operating system Microsoft Windows Server 2012 R2 Data Center Edition
Virtual processors per virtual machine 1
RAM per virtual machine 2 GB
Available storage capacity per virtual machine 100 GB
IOPS per virtual machine 25
I/O pattern Random
I/O read/write ratio 2:1
This specification for a virtual machine does not represent any specific application. Rather, it represents a single common point of reference by which to measure other virtual machines.
Overview
Defining the reference workload
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Applying the reference workload
When you consider an existing server for movement into a virtual infrastructure, you have the opportunity to gain efficiency by right-sizing the virtual hardware resources assigned to that system.
The solution creates a pool of resources that are sufficient to host a target number of reference virtual machines with the characteristics shown in Table 10. Virtual
machines may not exactly match the specifications. In that case, define a single specific customer virtual machine as the equivalent of some number of reference virtual machines together, and assume these virtual machines are in use in the pool. Continue to provision virtual machines from the resource pool until no resources remain.
A small custom-built application server must move into this virtual infrastructure. The physical hardware that supports the application is not fully used. A careful analysis of the existing application reveals that the application can use one processor and needs 3 GB of memory to run normally. The I/O workload ranges between 4 IOPS at idle time to a peak of 15 IOPS when busy. The entire application consumes about 30 GB on local hard drive storage.
Based on these numbers, the resource pool needs the following resources: CPU of one reference virtual machine
Memory of two reference virtual machines Storage of one reference virtual machine I/Os of one reference virtual machine
In this example, an appropriate virtual machine uses the resources for two of the reference virtual machines. If implemented on a VNX5400 storage system, which can support up to 300 virtual machines, resources for 298 reference virtual machines remain.
The database server for a customer’s point-of-sale system must move into this virtual infrastructure. It is currently running on a physical system with four CPUs and 16 GB of memory. It uses 200 GB of storage and generates 200 IOPS during an average busy cycle.
The requirements to virtualize this application are: CPUs of four reference virtual machines Memory of eight reference virtual machine Storage of two reference virtual machines I/Os of eight reference virtual machines
In this case, the one appropriate virtual machine uses the resources of eight
reference virtual machines. If implemented on a VNX5400 storage system, which can Overview Example 1: Custom-built application Example 2: Point of sale system
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support up to 300 virtual machines, resources for 292 reference virtual machines remain.
The customer’s web server must move into this virtual infrastructure. It is currently running on a physical system with two CPUs and 8 GB of memory. It uses 25 GB of storage and generates 50 IOPS during an average busy cycle.
The requirements to virtualize this application are: CPUs of two reference virtual machines Memory of four reference virtual machines Storage of one reference virtual machine I/Os of two reference virtual machines
In this case, the one appropriate virtual machine uses the resources of four reference virtual machines. If implemented on a VNX5400 storage system which can support up to 300 virtual machines, resources for 296 reference virtual machines remain.
The database server for a customer’s decision support system must move into this virtual infrastructure. It is currently running on a physical system with 10 CPUs and 64 GB of memory. It uses 5 TB of storage and generates 700 IOPS during an average busy cycle.
The requirements to virtualize this application are: CPUs of 10 reference virtual machines Memory of 32 reference virtual machines Storage of 52 reference virtual machines I/Os of 28 reference virtual machines
In this case, one virtual machine uses the resources of 52 reference virtual machines. If implemented on a VNX5400 storage system, which can support up to 300 virtual machines, resources for 248 reference virtual machines remain.
These four examples illustrate the flexibility of the resource pool model. In all four cases, the workloads reduce the amount of available resources in the pool. All four examples can be implemented on the same virtual infrastructure with an initial capacity for 300 reference virtual machines, and resources for 234 reference virtual machines remain in the resource pool as shown in Figure 36.
Figure 36. Resource pool flexibility
Example 3: Web server Example 4: Decision-support database Summary of examples
95 EMC VSPEX Private Cloud: VMware vSphere 5.5 for up to 1,000 Virtual Machines Enabled by Mircosoft Windows Server 2012 R2, EMc VNX Series, and EMc Powered Backup-Proven Infrastructure Guide In more advanced cases, there may be tradeoffs between memory and I/O or other relationships where increasing the amount of one resource decreases the need for another. In these cases, the interactions between resource allocations become highly complex, and are beyond the scope of the document. Examine the change in resource balance and determine the new level of requirements. Add these virtual machines to the infrastructure with the method described in the examples.