Virtustream Blog

What is a MicroVM (µVM)?


in Business, µVM, Cloud, Technology

By Dave Henry, Technical Product Marketing, @davemhenry

Virtustream MicroVM™, or µVM™, is an incredibly cool, surprisingly simple, yet often misunderstood piece of cloud technology. There seems to be some confusion about the MicroVM’s function, and even what it actually is – so much confusion, in fact, that I believe some folks might not understand the full benefits that Virtustream MicroVM can give them.

MicroVM as a Unit of Measure

A MicroVM is a unit of measure that summarizes cloud computing resource consumption. Virtustream uses this measurement of resource consumption to determine a customer’s monthly bill. This is similar to how your electric company bills you based on the amount of electrical current you actually use, rather than the number of power outlets you have, or the electrical devices you own. Virtustream doesn’t bill based on instance size or resources allocated, but instead bills based on the amount of cloud computing resources you actually use.

A MicroVM is calculated from other measurements. This isn’t so unusual – many measurements are calculated from other measurements, for example Miles per Gallon (MPG) is the measure of distance traveled divided by the amount of fuel consumed, and the volume of a rectangular solid is its height multiplied by its width multiplied by its depth, given as cubic inches or feet or as cubic centimeters or meters as appropriate.

Just as MPG is a measure of two dimensions and volume is a measure of three dimensions, MicroVMs are a measure of four “dimensions” of resource consumption. A MicroVM takes measurements at the hypervisor level of a virtual machine’s CPU usage, memory usage, storage I/O per second, and network bandwidth usage.

Unlike the other multi-dimension measurements for MPG and Volume, calculating MicroVMs of resource consumption for a virtual machine is mathematically much easier. Determining a “MicroVMs’ worth” of each of the four dimensions is measured as follows:

  • CPU usage in increments of 768MHz
  • Memory usage in increments of 2GB
  • Storage IOPS in increments to 40
  • Network bandwidth usage in increments of 2MBps

Then, whichever of these four dimensions of the MicroVM is largest becomes the MicroVM measurement at that moment, as shown in Figure One below.

Figure One: MicroVMs as Measured for Individual Virtual Machines

Figure One shows the MicroVM measurements taken on four different virtual machines. xStream, our cloud management platform, takes these measurements at the hypervisor level on all virtual machines running in Virtustream Enterprise Cloud.

By totaling the MicroVM measurements, we see that, at this moment, the four virtual machines are using 14 MicroVMs’ worth of cloud resources.

MicroVM Classes

Of course, real-world IT isn’t quite so simple and straight-forward, and not all cloud resources are created equal. Different customers have different needs for their virtual machines, and often a single customer has different needs for different virtual machines.

In order to meet these needs, Virtustream has identified multiple classes of virtual machines. We use these classifications to assign virtual machines to the infrastructure that best serves their respective needs. Some considerations that go into determining a VM’s Class include:

  • Does the VM require access to the Internet, or should it be isolated from outside connections?
  • Is the VM standalone, or will it be replicated so it can failover to another data center?
  • Does the VM have a requirement for a large amount of memory (more than 64GB)?

All of a customer’s VMs in a particular class are run within different zones of our infrastructure, ensuring we’re able to best meet the customer’s needs. For example, VMs that do not require Internet access are run on infrastructure that has no connections to the Internet, helping to ensure greater security.

To simplify billing across the different Classes, MicroVM measurements are aggregated across all VMs within each Class. This is accomplished by combining the measurements from each VM into a single measurement. The measurements for CPU usage are combined, as are the measurements for memory, storage IOPS, and network bandwidth usage. These combined measurements are then used to calculate a single MicroVM number for all VMs in that Class.

Figure Two below shows how this aggregation would be done for the four virtual machines used as the example in Figure One.

Figure Two: MicroVMs as Measured Across Virtual Machines in the Same Class

Figure Two shows all of the four dimensions of the MicroVM measurements for the four virtual machines shown in Figure One, combined for each dimension. Combined, all four VMs are currently using eight MicroVMs’ worth of CPU. Since that is the largest of the four dimensions at the time of this measurement, this customer would be measured as consuming 8 MicroVMs across the entire Class.

It’s pretty easy to see how this aggregation benefits Virtustream customers – eight MicroVMs across the entire class is approximately 42% lower than the 14 MicroVMs when measured individually.

What Our Customers See

Virtustream customers see MicroVM measurements in two different ways.

First, customers receive reports showing all MicroVM usage on a per-VM basis for all VMs they have hosted in Virtustream Enterprise Cloud. This allows customers to easily determine which VMs are the largest consumers of resources, and can provide clear starting points for optimization efforts.

Secondly, Virtustream uses MicroVMs to calculate customers’ monthly bills. As we discussed earlier, your electric company doesn’t bill you based on kilowatts, but instead uses the meter’s measurement of kilowatt-hours. Virtustream uses a similar approach and bills based on MicroVM-Hours. Virtustream measures MicroVMs of resource consumption every five minutes (as in Figure One), and uses those numbers to calculate the MicroVMs of resource consumption for the entire Class (as in Figure Two). Twelve consecutive measurements are then averaged to calculate the MicroVM-Hours consumed by all of the customer’s VMs in that Class during that hour. The monthly bill for each Class totals all the MicroVM-Hours consumed by that Class during the month.

To Sum Up

In all, it’s easy to see how the MicroVM:

  • Allows Virtustream to avoid use of pre-sized instances
  • Frees customers from concerns about “one size fits some” VMs
  • Provides customers with cost savings through a combination of aggregation and only charging based upon cloud compute resources they actually use.

If you’d like to learn how your organization can start to benefit from MicroVM technology, contact your Virtustream account manager or reseller partner today. Tell ‘em Dave sent you.