Use cases and implications of creating limits and reservations in VMware vSphere 6.
- [Voiceover] In this video I'll explain…reservations and limits.…A reservation is a guarantee of either…memory or CPU for a virtual machine.…You can set a specific reservation…in megabytes or in megahertz.…Remember that CPU and memory are allocated…to virtual machines, but are not necessarily guaranteed…unless you configure a reservation.…Think of it this way, let's say you buy an eight cut pizza,…and you tell five people,…"You cannot eat more than two slices".…You're hoping that some people…may actually only want one slice,…and that everyone will end up happy,…and this is a classic example of oversubscription.…
Now if you set aside two pieces…for someone who you know is really hungry,…you're creating a reservation,…and this is good for the really hungry person,…but bad for everyone else who is sharing that pizza.…You can reserve memory and CPU in the same way.…A limit places a hard cap on the amount of resources…that a virtual machine can use.…You can set CPU and memory limits on a virtual machine,…but why would I ever use a limit?…
VMware Certified Instructor Rick Crisci provides an overview of vSphere resource controls—shares, limits, and reservations—and their impact on performance and VSWP file size. Rick explains exactly what happens when virtual machines compete for resources, the role of swap files, and how resource controls help automate allocation.
In chapter 2, Rick shows how to manage performance with resource pools, including child pools. He explains the impact a reservation has on resource pools, and includes a demo on creating and configuring a resource pool. Chapter 3 is an overview of the vFlash architecture for leveraging SSD resources. Watch this chapter to learn how to configure vFlash reservations and to assign a reservation to a VM.
Note: This course maps to the Administer and Manage vSphere 6.x Resources domain of the vSphere Certified Professional 6—Data Center Virtualization (VCP6DCV) exam.
- Allocating memory and CPU
- Using ESXTOP
- Configuring reservations, limits, and shares
- Managing performance with resource pools
- Creating child and tiered resource pools
- Leveraging SSD resources with vFlash