Term
| What is the difference between Static Entitlement and Dynamic Entitlement |
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Definition
| Static entitlement is user-defined. Dynamic entitlement is calculated by the DRS cluster and by the host local schedulers. |
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Term
| How does dynamic entitlement work? |
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Definition
| The host-local CPU scheduler and the host-local memory scheduler calculate entitlements. Dynamic entitlement is flexible and will increase/decrease based on virtual machine demand, but will never increase past it's configured CPU/Memory size |
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Term
| How is Dynamic CPU entitlement calculated |
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Definition
| Based on teh active CPU, which is taken from %Run +%Ready MHz metrics of that virtual machine |
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Term
| How is Memory Entitlement calculated? |
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Definition
| Based on active memory - the working memory set of the VM (actual physical RAM pages); Memory overhead; 25% of the idle memory |
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Term
| Name the three settings you can assign in Static entitlement |
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Definition
| Shares, Reservations, Limits |
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Term
| Describe how shares are allocated |
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Definition
* Shares specify the relative importance of a VM (or resource pool). I.E. If one VM has twice as many shares as another, then it is entitled to twice as much of the resource when contention occurs.
* Shares can be set in a High, Medium, Low, or Custom. Which map relatively to 4:2:1
* High – 2000 shares/CPU, 20 shares/MB of configured VM Memory
* Medium – 1000 shares/CPU, 10 shares/MB of configured VM Memory
* Low – 500 shares/CPU, 5 shares/MB of configured VM Memory.
* Custom – specified by the user – beware as VMs become powered on and off this value stays the same.
* Shares only make senses when applied at a sibling level. So a parent container can be assigned a share, and all the child objects are assigned shares within it that correspond to their relative importance within the parent container.
* Apply only to powered on VMs
* When a new VM is powered on, the relative priority of all other VMs that are siblings will change.
Source: blog.mwpreston.net |
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Term
| Describe how Reservations are allocated |
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Definition
* Reservations specify the guaranteed minimum allocation or resources for a VM
* You may only power on a VM if there is enough unreserved resources to meet the VMs reservation.
* The host will guarantee the reservation, even when contention occurs.
* Reservations are specified in concrete units and by default are set to 0.
Source: blog.mwpreston.net |
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Term
| Describe how Limits are allocated |
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Definition
* Limits specify the upper bound for CPU, Memory, or storage I/O that can be allocated.
* A host can always allocate more resources than a VMs reservation, but never more than a VMs limit, whether contention is occurring or not.
* Expressed in concrete Units.
* Default is unlimited and in most cases there is no need to use this.
* Benefits – does allow you to simulate having few resources or contention.
* Drawbacks – could waste idle resources. Resources can not be assigned above a VMs limit even if they are available.
Source: blog.mwpreston.net |
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Term
| What happens when a new VM is powered on in a sibling level where shares are allocated |
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Definition
| The relative priority of all other VMs that are siblings will change |
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Term
| What is the default VM reservation? |
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Definition
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Term
| T/F: A VM cannot exceed it's VM reservation |
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Definition
| False - reservations specify the guaranteed minimum allocation or resources for a VM. They can be exceeded |
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Term
| T/F: A VM cannot exceed it's limit |
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Definition
| True - A host can always allocate more resources than a VMs reservation, but never more than a VMs limit, whether contention is occuring or not |
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Term
| What is the default limit on VMs |
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Definition
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Term
| T/F: Reservations are ignored in the case of resource contention |
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Definition
| False: Reservations are guaranteed, even when resource contention occurs |
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