Vmware Ha Slot Size Calculations

In vSphere 5.1, you can set these values in the cluster settings in the vSphere Web Client, under Slot Size policy and Fixed slot size. Note: Configuration this way sets the exact value. To set the slot size: In the vSphere Web Client, browse to the vSphere HA cluster. Click the Manage tab and click Settings. Under Settings, select HA and click. To see the slot size information click on the blue 'Advanced Runtime Info' link. The Slot size is calculated by the CPU and Memory Reservations at the individual Virtual Machine level in the whole cluster, the largest VM's CPU and Memory reservation determines the slot size. For more information on the slot size calculations on the different.

1. Vmware Ha Slot Size Calculations Formula
2. Vmware Ha Slot Size Calculations Cheat
3. Vmware Ha Slot Size Calculations Calculator
4. Vsphere Ha Slot Size 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.

Setting Alarms to Monitor Cluster Changes

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. Thai slot machine.

Several default vSphere HA alarms are available.

• Insufficient failover resources (a cluster alarm)
• Cannot find primary (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)

Monitoring Cluster Validity

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.

DRS behavior is not affected if a cluster is red because of a vSphere HA issue.

vSphere HA and Storage vMotion Interoperability in a Mixed Cluster

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.

Admission Control Best Practices

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. 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.

Using Auto Deploy with vSphere HA

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.

Upgrading Hosts in a Cluster Using Virtual SAN

Vmware Ha Slot Size Calculations Formula

Vmware Ha Slot Size Calculations Cheat

1. Upgrade all of the hosts.
2. Disable vSphere HA.
3. Enable Virtual SAN.
4. Re-enable vSphere HA.

Do you have HA enabled cluster ? If you do then you will need to know what a slot size is, that's if you don't already, if you do already then just cut straight to the cool PowerCLI example….

I'm not going to explain this completely as I could never write such an excellent explanation as Duncan over at Yellow bricks, I highly recommend reading this post as it is pure excellence.

1. Vmware Ha Slot Size Calculations Formula
2. Vmware Ha Slot Size Calculations Cheat
3. Vmware Ha Slot Size Calculations Calculator
4. Vsphere Ha Slot Size 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.

Setting Alarms to Monitor Cluster Changes

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. Thai slot machine.

Several default vSphere HA alarms are available.

• Insufficient failover resources (a cluster alarm)
• Cannot find primary (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)

Monitoring Cluster Validity

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.

DRS behavior is not affected if a cluster is red because of a vSphere HA issue.

vSphere HA and Storage vMotion Interoperability in a Mixed Cluster

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.

Admission Control Best Practices

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. 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.

Using Auto Deploy with vSphere HA

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.

Upgrading Hosts in a Cluster Using Virtual SAN

Vmware Ha Slot Size Calculations Formula

Vmware Ha Slot Size Calculations Cheat

1. Upgrade all of the hosts.
2. Disable vSphere HA.
3. Enable Virtual SAN.
4. Re-enable vSphere HA.

Do you have HA enabled cluster ? If you do then you will need to know what a slot size is, that's if you don't already, if you do already then just cut straight to the cool PowerCLI example….

I'm not going to explain this completely as I could never write such an excellent explanation as Duncan over at Yellow bricks, I highly recommend reading this post as it is pure excellence.

So what is a slot size ?

If you have a HA enabled cluster and have set the admission control to ‘Prevent VMs from being powered on if they violate availability constraints', this means when your cluster does not have enough room to start VMs if a host fails then you will violate the constraints of the cluster and vCenter will not allow you to power on your next VM, but how does it know when you do not have enough room for another VM to power on ?

Enter slot's, a slot is measurement, the measurement is made up of a CPU Mhz reservation and Memory reservation, if there is no reservation a default of 256Mhz will be used for the CPU and the for the memory the memory overhead will be used, to make sure the cluster has enough room it will always look for a worst case CPU reservation and a worst case memory reservation scenario, so if you have a number of VMs in the cluster vCenter will base your slot size on the worst case MHZ and MB you have, if you have 50 x 2Ghz reserved, 4GB reserved web servers and 1 x 4Ghz reserved, 3GB reserved SQL server the slot size will be based on 4Ghz and 4GB, and how many of these can be fit into the cluster.

It depends on your thoughts as to whether you think this is a good way of working this out or if this not, would you base it on an average CPU and memory across all of your VM's ? Personally I can see why VMware have done this as they need to know that the VMs will have enough room to power on if there is a host failure. Don't forget, if you think you know better then you can change the advanced configuration for VMware HA by following this guide.

Again, I highly recommend reading both Duncan's HA Deep Dive post and his recent slot size post as I have just touched on the subject (and missed all the main details).

So anyway, where does PowerCLI fit in ?

With the following script you can view the slot information, you can see how many slots are available for each cluster and also the CPU and Memory details:

Please note that this information unfortunately is not in the 3.5 API so this code will only work on vSphere.

Example Output:

Vmware Ha Slot Size Calculations Calculator

Cluster : Production
TotalSlots : 32
UsedSlots : 10
AvailableSlots : 22
SlotNumvCPUs : 1
SlotCPUMHz : 256
SlotMemoryMB : 118

And here is the code:

So what if you use the VESI ?

Vsphere Ha Slot Size Calculation

Ok, I have decided to start adding my little code snippets to a PowerPack which I will keep in a central place on my site and upload with all my little on-liners and scripts, you can download my custom PowerPack, import it into the VESI and suddenly you will have more actions available to you, the first in this PowerPack is available under the Clusters node as seen below:

Just select a cluster, or multiple clusters and click Slot Information, you will then see the information displayed in the VESI interface:

Keep an eye out on my site for more VESI integrations, expanding the already amazing product into further regions.