Jun 28, 2017 How does it calculate and our mind will think of the below calculation Available slots = Total slot – Used slots i,e Available slots = 234 – 6 = 228. It should come as 228 as available slots but why Available slots is 150 in the above snapshot. Is that wrong or VMware did something wrong in HA slot calculation?
To ensure optimal vSphere HA cluster performance, you should follow certain best practices. This topic highlights some of the key best practices for a vSphere HA cluster. You can also refer to the vSphere High Availability Deployment Best Practices publication for further discussion.
My slot size is 32Mhz/80MB. Maximum number of CPU slots I can have is 328.25. Maximum number of RAM slots 40963/80=512.0375 which defines the number of total slots as HA chooses the most restrictive number (a worst case scenario). As you can see HA shows 511 total slots in the cluster. If you have the VM configured with the highest memory reservation of 8192 MB (8 GB) and highest CPU reservation of 4096 MHZ. Among the other VM's in the cluster, then the slot size for memory is 8192 MB and slot size for CPU is 4096 MHZ. VMware HA slot calculation is done by the vCenter HA service that provides the capacity of the cluster as a whole to the various agents involved. In VirtualCenter 2.x, the virtual machine with the maximum resource consumption was the one chosen as the basis of the slot calculation. The total amount of available resources in the cluster will be divided by the slot size and that dictates how many VMs can be powered on without violating availability constraints. Meaning that it will guarantee that every powered on virtual machine can be failed over. As said this slot is dictated by the worst case reservation for CPU and Memory.
VMware HA Slot is the default admission control option prior to vSphere 6.5. Slot Size is defined as the memory and CPU resources that satisfy the reservation requirements for any powered-on virtual machines in the HA cluster.This article is just to cover how the HA slots are calculated step by step not more than that. For the second image, the cluster has two host and below is the configuration. If I go to run time info of cluster in vmware I can it has used 32MHz 1, Virtual CPU and 40MB memory slot size. Then it says total slot is 691 and failover slot is 422.
When vSphere HA or Fault Tolerance take action to maintain availability, for example, a virtual machine failover, you can be notified about such changes. Configure alarms in vCenter Server to be triggered when these actions occur, and have alerts, such as emails, sent to a specified set of administrators.
Several default vSphere HA alarms are available.
Insufficient failover resources (a cluster alarm) | |
Cannot find master(a cluster alarm) | |
■ | Failover in progress(a cluster alarm) |
Host HA status(a host alarm) | |
VM monitoring error(a virtual machine alarm) | |
VM monitoring action (a virtual machine alarm) Casino rama concert schedule. | |
■ | Failover failed (a virtual machine alarm) |
The default alarms include the feature name, vSphere HA.
A valid cluster is one in which the admission control policy has not been violated.
A cluster enabled for vSphere HA becomes invalid when the number of virtual machines powered on exceeds the failover requirements, that is, the current failover capacity is smaller than configured failover capacity. If admission control is disabled, clusters do not become invalid.
In the vSphere Web Client, select vSphere HA from the cluster's Monitor tab and then select Configuration Issues. A list of current vSphere HA issues appears.
In the vSphere Client, the cluster's Summary tab displays a list of configuration issues for clusters. The list explains what has caused the cluster to become invalid or overcommitted.
DRS behavior is not affected if a cluster is red because of a vSphere HA issue.
In clusters where ESXi 5.x hosts and ESX/ESXi 4.1 or prior hosts are present and where Storage vMotion is used extensively or Storage DRS is enabled, do not deploy vSphere HA. vSphere HA might respond to a host failure by restarting a virtual machine on a host with an ESXi version different from the one on which the virtual machine was running before the failure. A problem can occur if, at the time of failure, the virtual machine was involved in a Storage vMotion action on an ESXi 5.x host, and vSphere HA restarts the virtual machine on a host with a version prior to ESXi 5.0. While the virtual machine might power on, any subsequent attempts at snapshot operations could corrupt the vdisk state and leave the virtual machine unusable.
The following recommendations are best practices for vSphere HA admission control.
Select the Percentage of Cluster Resources Reserved admission control policy. This policy offers the most flexibility in terms of host and virtual machine sizing. When configuring this policy, choose a percentage for CPU and memory that reflects the number of host failures you want to support. For example, if you want vSphere HA to set aside resources for two host failures and have ten hosts of equal capacity in the cluster, then specify 20% (2/10). | |
Ensure that you size all cluster hosts equally. For the Host Failures Cluster Tolerates policy, an unbalanced cluster results in excess capacity being reserved to handle failures because vSphere HA reserves capacity for the largest hosts. Macam macam slot dan socket pada mainboard. For the Percentage of Cluster Resources Policy, an unbalanced cluster requires that you specify larger percentages than would otherwise be necessary to reserve enough capacity for the anticipated number of host failures. | |
■ | If you plan to use the Host Failures Cluster Tolerates policy, try to keep virtual machine sizing requirements similar across all configured virtual machines. This policy uses slot sizes to calculate the amount of capacity needed to reserve for each virtual machine. The slot size is based on the largest reserved memory and CPU needed for any virtual machine. When you mix virtual machines of different CPU and memory requirements, the slot size calculation defaults to the largest possible, which limits consolidation. |
If you plan to use the Specify Failover Hosts policy, decide how many host failures to support and then specify this number of hosts as failover hosts. If the cluster is unbalanced, the designated failover hosts should be at least the same size as the non-failover hosts in your cluster. This ensures that there is adequate capacity in case of failure. |
You can use vSphere HA and Auto Deploy together to improve the availability of your virtual machines. Auto Deploy provisions hosts when they power up and you can also configure it to install the vSphere HA agent on such hosts during the boot process. See the Auto Deploy documentation included in vSphere Installation and Setup for details.
To ensure optimal vSphere HA cluster performance, VMware recommends that you follow certain best practices. Networking configuration and redundancy are important when designing and implementing your cluster.
When vSphere HA or Fault Tolerance take action to maintain availability, for example, a virtual machine failover, you can be notified about such changes. Configure alarms in vCenter Server to be triggered when these actions occur, and have alerts, such as emails, sent to a specified set of administrators.
Several default vSphere HA alarms are available.
Insufficient failover resources (a cluster alarm) | |
Cannot find master(a cluster alarm) | |
■ | Failover in progress(a cluster alarm) |
Host HA status(a host alarm) | |
VM monitoring error(a virtual machine alarm) | |
VM monitoring action (a virtual machine alarm) | |
■ | Failover failed (a virtual machine alarm) |
The default alarms include the feature name, vSphere HA.
A valid cluster is one in which the admission control policy has not been violated.
A cluster enabled for vSphere HA becomes invalid (red) when the number of virtual machines powered on exceeds the failover requirements, that is, the current failover capacity is smaller than configured failover capacity. If admission control is disabled, clusters do not become invalid.
The cluster's Summary tab in the vSphere Client displays a list of configuration issues for clusters. The list explains what has caused the cluster to become invalid or overcommitted (yellow).
Vmware Cluster Slot Size Calculation Calculator
DRS behavior is not affected if a cluster is red because of a vSphere HA issue.
Configuration issues and other errors can occur for your cluster or its hosts that adversely affect the proper operation of vSphere HA. You can monitor these errors by looking at the Cluster Operational Status screen, which is accessible in the vSphere Client from the vSphere HA section of the cluster's Summary tab. Address issues listed here.
Vmware High Availability Best Practices
Most configuration issues have a matching event that is logged. All vSphere HA events include 'vSphere HA' in the description. You can search for this term to find the corresponding events.
In clusters where ESXi 5.0 hosts and ESX/ESXi 4.1 or prior hosts are present and where Storage vMotion is used extensively or Storage DRS is enabled, VMware recommends that you do not deploy vSphere HA. vSphere HA might respond to a host failure by restarting a virtual machine on a host with an ESXi version different from the one on which the virtual machine was running before the failure. A problem can occur if, at the time of failure, the virtual machine was involved in a Storage vMotion action on an ESXi 5.0 host, and vSphere HA restarts the virtual machine on a host with a version prior to ESXi 5.0. While the virtual machine might power on, any subsequent attempts at snapshot operations could corrupt the vdisk state and leave the virtual machine unusable.
The following recommendations are best practices for vSphere HA admission control.
In the vSphere Web Client, select vSphere HA from the cluster's Monitor tab and then select Configuration Issues. A list of current vSphere HA issues appears.
In the vSphere Client, the cluster's Summary tab displays a list of configuration issues for clusters. The list explains what has caused the cluster to become invalid or overcommitted.
DRS behavior is not affected if a cluster is red because of a vSphere HA issue.
In clusters where ESXi 5.x hosts and ESX/ESXi 4.1 or prior hosts are present and where Storage vMotion is used extensively or Storage DRS is enabled, do not deploy vSphere HA. vSphere HA might respond to a host failure by restarting a virtual machine on a host with an ESXi version different from the one on which the virtual machine was running before the failure. A problem can occur if, at the time of failure, the virtual machine was involved in a Storage vMotion action on an ESXi 5.x host, and vSphere HA restarts the virtual machine on a host with a version prior to ESXi 5.0. While the virtual machine might power on, any subsequent attempts at snapshot operations could corrupt the vdisk state and leave the virtual machine unusable.
The following recommendations are best practices for vSphere HA admission control.
Select the Percentage of Cluster Resources Reserved admission control policy. This policy offers the most flexibility in terms of host and virtual machine sizing. When configuring this policy, choose a percentage for CPU and memory that reflects the number of host failures you want to support. For example, if you want vSphere HA to set aside resources for two host failures and have ten hosts of equal capacity in the cluster, then specify 20% (2/10). | |
Ensure that you size all cluster hosts equally. For the Host Failures Cluster Tolerates policy, an unbalanced cluster results in excess capacity being reserved to handle failures because vSphere HA reserves capacity for the largest hosts. Macam macam slot dan socket pada mainboard. For the Percentage of Cluster Resources Policy, an unbalanced cluster requires that you specify larger percentages than would otherwise be necessary to reserve enough capacity for the anticipated number of host failures. | |
■ | If you plan to use the Host Failures Cluster Tolerates policy, try to keep virtual machine sizing requirements similar across all configured virtual machines. This policy uses slot sizes to calculate the amount of capacity needed to reserve for each virtual machine. The slot size is based on the largest reserved memory and CPU needed for any virtual machine. When you mix virtual machines of different CPU and memory requirements, the slot size calculation defaults to the largest possible, which limits consolidation. |
If you plan to use the Specify Failover Hosts policy, decide how many host failures to support and then specify this number of hosts as failover hosts. If the cluster is unbalanced, the designated failover hosts should be at least the same size as the non-failover hosts in your cluster. This ensures that there is adequate capacity in case of failure. |
You can use vSphere HA and Auto Deploy together to improve the availability of your virtual machines. Auto Deploy provisions hosts when they power up and you can also configure it to install the vSphere HA agent on such hosts during the boot process. See the Auto Deploy documentation included in vSphere Installation and Setup for details.
To ensure optimal vSphere HA cluster performance, VMware recommends that you follow certain best practices. Networking configuration and redundancy are important when designing and implementing your cluster.
When vSphere HA or Fault Tolerance take action to maintain availability, for example, a virtual machine failover, you can be notified about such changes. Configure alarms in vCenter Server to be triggered when these actions occur, and have alerts, such as emails, sent to a specified set of administrators.
Several default vSphere HA alarms are available.
Insufficient failover resources (a cluster alarm) | |
Cannot find master(a cluster alarm) | |
■ | Failover in progress(a cluster alarm) |
Host HA status(a host alarm) | |
VM monitoring error(a virtual machine alarm) | |
VM monitoring action (a virtual machine alarm) | |
■ | Failover failed (a virtual machine alarm) |
The default alarms include the feature name, vSphere HA.
A valid cluster is one in which the admission control policy has not been violated.
A cluster enabled for vSphere HA becomes invalid (red) when the number of virtual machines powered on exceeds the failover requirements, that is, the current failover capacity is smaller than configured failover capacity. If admission control is disabled, clusters do not become invalid.
The cluster's Summary tab in the vSphere Client displays a list of configuration issues for clusters. The list explains what has caused the cluster to become invalid or overcommitted (yellow).
Vmware Cluster Slot Size Calculation Calculator
DRS behavior is not affected if a cluster is red because of a vSphere HA issue.
Configuration issues and other errors can occur for your cluster or its hosts that adversely affect the proper operation of vSphere HA. You can monitor these errors by looking at the Cluster Operational Status screen, which is accessible in the vSphere Client from the vSphere HA section of the cluster's Summary tab. Address issues listed here.
Vmware High Availability Best Practices
Most configuration issues have a matching event that is logged. All vSphere HA events include 'vSphere HA' in the description. You can search for this term to find the corresponding events.
In clusters where ESXi 5.0 hosts and ESX/ESXi 4.1 or prior hosts are present and where Storage vMotion is used extensively or Storage DRS is enabled, VMware recommends that you do not deploy vSphere HA. vSphere HA might respond to a host failure by restarting a virtual machine on a host with an ESXi version different from the one on which the virtual machine was running before the failure. A problem can occur if, at the time of failure, the virtual machine was involved in a Storage vMotion action on an ESXi 5.0 host, and vSphere HA restarts the virtual machine on a host with a version prior to ESXi 5.0. While the virtual machine might power on, any subsequent attempts at snapshot operations could corrupt the vdisk state and leave the virtual machine unusable.
The following recommendations are best practices for vSphere HA admission control.
Select the Percentage of Cluster Resources Reserved admission control policy. This policy offers the most flexibility in terms of host and virtual machine sizing. In most cases, a calculation of 1/N, where N is the number of total nodes in the cluster, yields adequate sparing. | |
Ensure that you size all cluster hosts equally. An unbalanced cluster results in excess capacity being reserved to handle failure of the largest possible node. | |
■ | Try to keep virtual machine sizing requirements similar across all configured virtual machines. The Host Failures Cluster Tolerates admission control policy uses slot sizes to calculate the amount of capacity needed to reserve for each virtual machine. The slot size is based on the largest reserved memory and CPU needed for any virtual machine. When you mix virtual machines of different CPU and memory requirements, the slot size calculation defaults to the largest possible, which limits consolidation. |
You can use vSphere HA and Auto Deploy together to improve the availability of your virtual machines. Auto Deploy provisions hosts when they power up and you can also configure it to install the vSphere HA agent on such hosts during the boot process. To have Auto Deploy install the vSphere HA agent, the image profile you assign to the host must include the vmware-fdm VIB. See the Auto Deploy documentation included in vSphere Installation and Setup for details.
Network Availability Calculation
Vmware Vcenter High Availability
If you need to perform network maintenance that might trigger host isolation responses, VMware recommends that you first suspend vSphere HA by disabling Host Monitoring. After the maintenance is complete, reenable Host Monitoring.
VMWare vShpere Slot Calculation
As per VMWare's Definition,
'A slot is a logical representation of the memory and CPU resources that satisfy the requirements for any powered-on virtual machine in the cluster.'
If you have configured reservations at VM level, It influence the HA slot calculation. Highest memory reservation and highest CPU reservation of the VM in your cluster determines the slot size for the cluster.
Here is the Example,
If you have the VM configured with the highest memory reservation of 8192 MB (8 GB) and highest CPU reservation of 4096 MHZ. among the other VM's in the cluster, then the slot size for memory is 8192 MB and slot size for CPU is 4096 MHZ. in the cluster.
If no VM level reservation is configured , Minimum CPU size of 256 MHZ and memory size of 0 MB + VM memory overhead will be considered as CPU and Memory slot size.
Calculation for Number of Slots in cluster :-
Once we got the Slot size for memory and CPU by the above method , Use the below calculation
Num of CPU Slots = Total available CPU resource of ESX or cluster / CPU Slot Size
Num of memory slots = Total available memory resource of ESX or cluster minus memory used for service console & ESX system / Memory Slot size
Let's take a Example,
I have 3 host on the cluster and 6 Virtual machine is running on the cluster and Each host capacity as follows
RAM = 50 GB per Host
CPU = 8 X 2.666 GHZ per host
Cluster RAM Resources = 50 X 3 = 150 GB - Memory for service console and system = 143 GB
Cluster CPU resources = 8 X 2.6 X 3 = 63 GHZ (63000 MHZ) of total CPU capacity in the cluster - CPU Capacity used by the ESX System = 60384 MHZ
I don't have any memory or CPU reservation in my cluster, So, the default CPU slot size 256 MHZ and one of my Virtual machine is assigned with 8 vcpu and its memory overhead is 344.98 MB (which is the highest overhead among my 6 virtual machines in the cluster)
Let's calculate the num of CPU & Memory slots
Num of CPU Slots = Total available CPU resource of cluster / CPUSlot size in MHZ
No of CPU Slots = 60384 MHZ / 256 MHZ = 235.875 Approx
Num of Memory Slots = Total available Memory resource of cluster / memory Slot Size in MB
Num of Memory Slots = 146432 / 345 = 424 Approx
The most restrictive number among CPU and Memory slots determines the amount of slots for this cluster. We have 235 slots available for CPU and 424 Slots available for Memory. So the most restrictive number is 235.
So, Total number of slots for my cluster is 235 Approx. Please find the below snapshot
Please refer my blog post on Understanding Total Slots, Used Slots & Available slots in VMware HA Slot to understand Total Slots, Used Slots & Available slots
I hope you understand the post..Thanks For Reading !!!!!
Vmware Cluster Slot Size Calculation Calculator
