Capacity Planning in a Virtual Environment

Capacity Planning in a Virtual Environment

Chris Chesley, Sr. Systems [email protected]

Balance

Capacity planning (from TechTarget) In information technology, capacity planning is the science and art of estimating the space, computer hardware, software and connection infrastructure resources that will be needed over some future period of time. A typical capacity concern of many enterprises is whether resources will be in place to handle an increasing number of requests as the number of users or interactions increase. The aim of the capacity planner is to plan so well that new capacity is added just in time to meet the anticipated need but not so early that resources go unused for a long period.

Summary: Capacity planning in a virtual environment is finding the balance between how many VMs can I run on my systems without having any performance issues with future growth taken into consideration.

Capacity Planning

1st step in capacity planning is resolving any performance issues

Resolving performance bottlenecks• Identify where you have performance issues (are VMs getting

needed resources)• Are the VMs getting the resources they need?• Quickly resolve current problems• Use proactive analysis to avoid future performance issues

Old vs. New

Pre-Virtualized Data Center• One application – One server• No sharing of memory and CPU• Limited sharing of storage

Virtualized Datacenter• Shared memory and CPU • Massively shared storage• Performance = capacity• Vmotion/DRS – Dynamic nature• Change from known to unknown state when VM added or changed

Takeaway

If not closely monitored and managed, sharing of resources will lead to performance problems and downtime.

Resource Utilization

What resources and metrics do I use? CPU

CPU usage CPU Ready %

Memory Memory Consumed

Disk Storage (how many GB am I using) I/O (reads, writes, disk latency, disk queue latency)

Physical Network

Capacity issues occur at any level or resource type VMs Host Cluster Resource Pools (Vmware only) Data Center

Boundaries in Virtual Environments

How to Identify Current Capacity Bottlenecks

Out of the box Management consoles: vCenter client (Vmware) and Hyper-V Manager or Virtual Machine Manager (Hyper-V):Real time per-host stats, per-cluster, and per-VM statistics

Esxtop (Vmware) or PerfMon (Hyper-V): per-host statistics

VIM API and SDK: allows software to collect only the statistics they want

Performance Monitoring Options

For every Cluster, Resource Pool, Host, and VM, using VirtualCenter to examine memory, storage, CPU and network utilization over a period of at least 1 week

Very time consuming process– (Clusters + Resource Pools + Hosts + VMs) X 5 resources (CPU, storage,

RAM, network, disk i/o) = # of charts to review– e.g. (3 Clusters +3 RPs+ 50 Hosts + 500 VMs) X 5 = 2,780 charts to examine

Requires ongoing attention: at least several times a week

Select a Cluster, Resource Pool, or a Host

Get info on available memory, storage, CPU, disk i/o, and network i/o

Apply an average VM footprint to every resource type to see which resource you will run out of first

That’s how many more VMs you can fit into Hosts, Clusters, or Resource Pools

Where do I put new VMs?

Identifying Available Resource Capacity

Model additions of new VMs Understand current utilization on all resource

types Make necessary changes to compensate for

current and future growth

Implement iron clad change control process Maintenance window and workload requirements Cluster failover configuration Resource Pool configuration Powered down VMs

Predicting Future Capacity Bottlenecks

Optimize your virtual machines• Very easy to create VMs, not easy to know how many

resources to give them.• No automated clean up• According to the Information Technology Infrastructure

Library (ITIL), capacity management is the discipline that ensures IT infrastructure is used in the most efficient, predictable and cost-effective manner.

• Goal of capacity management: Finding the balance between density and performance.

Optimize!2 nd step in capacity planning is making sure that you

are maximizing the number of VMs running on your hosts and clusters

Optimize your virtual environment• Insure that each VM is using the resources assigned to

them• Maximize your density of VMs per core or per host• Find wasted storage

Defining which Metrics to Monitor

Allocated vs. consumed resources.

CPU: The important metric to measure is CPU utilization.

Memory: Use memory consumed in most cases when evaluating memory utilization.

Memory consumed measures how much memory each VM is using on the physical host minus an memory that is shared by other VMs.

Storage: The best way to monitor storage is to look at each vmdk file from the guest OS perspective and look at utilization.

Identifying Allocated Resources

Allocated resources, limits and reservation info can be easily collected from vCenter or a 3rd party solution.

Defining your Evaluation Period

Time period: You need to decide how much data you need to analyze when computing the average or peak values to make sure that it captures your busy periods or is a good representation of your business cycles.

Priority: Many administrators will divide up their systems into high, medium and low priorities with different metrics for each group.

Computing Resources Consumed

The next step is to look at each resource and compute the average or peak utilization for your evaluation period.

Generate Recommendations

The next step is to put all the pieces together and evaluate each resource for each VM and determine if the right amount of CPU, Memory and Storage has been assigned to the VM.

Wasted Storage

• Easy to create VMs• VMs are large files• Not always easy to find any files that are not being

used.

Types of Wasted Storage

• Abandoned VMs – A virtual machine file that is on your datastore but is not attached to a VM listed in vCenter or the host.

• Powered off VMs• Templates Not used in 30 days or more• Snapshots• Zombie VMs – A virtual machine that is running but

not being used.

Wasted Storage

Abandoned VMs

Powered off VMs

Manual or Automated?

VKernel’s Optimization Pack and Capacity Analyzer does this work for you.

ConclusionThe goal of virtualization is to find the balance between correctly sizing your environment while achieving maximum performance with the least amount of resources.

Download a trial of VKernel’s appliances to resolve Performance bottlenecks and optimize your environment!

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