Vsphere Web Client Slot Size

With the slot policy option, vSphere HA admission control ensures that a specified number of hosts can fail and sufficient resources remain in the cluster to fail over all the virtual machines from those hosts.

Manage vSphere HA Slot Size; Configure a vSphere HA Cluster with Strict Admission Control; Lab 21: Implementing a vSphere DRS Cluster. Create a Load Imbalance; Create a vSphere DRS Cluster; Verify Proper vSphere DRS Cluster Functionality; Create, Test, and Disable a VM-VM Affinity Rule; Create, Test, and Disable an Anti-Affinity Rule. In vSphere 5.0 and newer, a slot size is set at the highest reservation of memory or CPU. If there are no reservations, CPU is set at 32 MHz and memory is 0MB + Overhead (as defined in the Resource Management Guide). For more information, see the VMware vSphere Availability guide. Apr 6, 2015 at 16:16 UTC. If you have Dell servers, you can always. give their support a jingle and get the recommended RAM population from the server team. They've been awesome to get this same info for our Dells (R710 and R620). assuming you have them under support.

Using the slot policy, vSphere HA performs admission control in the following way:

  1. Calculates the slot size.

    A slot is a logical representation of memory and CPU resources. By default, it is sized to satisfy the requirements for any powered-on virtual machine in the cluster.

  2. Determines how many slots each host in the cluster can hold.

  3. Determines the Current Failover Capacity of the cluster.

    This is the number of hosts that can fail and still leave enough slots to satisfy all of the powered-on virtual machines.

  4. Determines whether the Current Failover Capacity is less than the Configured Failover Capacity (provided by the user).

    If it is, admission control disallows the operation.

Note:

You can set a specific slot size for both CPU and memory in the admission control section of the vSphere HA settings in the vSphere Web Client.

Slot Size Calculation

Slot size is comprised of two components, CPU and memory.

  • vSphere HA calculates the CPU component by obtaining the CPU reservation of each powered-on virtual machine and selecting the largest value. If you have not specified a CPU reservation for a virtual machine, it is assigned a default value of 32MHz. You can change this value by using the das.vmcpuminmhz advanced option.)

  • vSphere HA calculates the memory component by obtaining the memory reservation, plus memory overhead, of each powered-on virtual machine and selecting the largest value. There is no default value for the memory reservation.

If your cluster contains any virtual machines that have much larger reservations than the others, they will distort slot size calculation. To avoid this, you can specify an upper bound for the CPU or memory component of the slot size by using the das.slotcpuinmhz or das.slotmeminmb advanced options, respectively. See vSphere HA Advanced Options.

You can also determine the risk of resource fragmentation in your cluster by viewing the number of virtual machines that require multiple slots. This can be calculated in the admission control section of the vSphere HA settings in the vSphere Web Client. Virtual machines might require multiple slots if you have specified a fixed slot size or a maximum slot size using advanced options.

Using Slots to Compute the Current Failover Capacity

After the slot size is calculated, vSphere HA determines each host's CPU and memory resources that are available for virtual machines. These amounts are those contained in the host's root resource pool, not the total physical resources of the host. The resource data for a host that is used by vSphere HA can be found on the host's Summary tab on the vSphere Web Client. If all hosts in your cluster are the same, this data can be obtained by dividing the cluster-level figures by the number of hosts. Resources being used for virtualization purposes are not included. Only hosts that are connected, not in maintenance mode, and that have no vSphere HA errors are considered.

The maximum number of slots that each host can support is then determined. To do this, the host’s CPU resource amount is divided by the CPU component of the slot size and the result is rounded down. The same calculation is made for the host's memory resource amount. These two numbers are compared and the smaller number is the number of slots that the host can support.

The Current Failover Capacity is computed by determining how many hosts (starting from the largest) can fail and still leave enough slots to satisfy the requirements of all powered-on virtual machines.

Admission Control Using Slot Policy

The way that slot size is calculated and used with this admission control policy is shown in an example. Make the following assumptions about a cluster:

  • The cluster is comprised of three hosts, each with a different amount of available CPU and memory resources. The first host (H1) has 9GHz of available CPU resources and 9GB of available memory, while Host 2 (H2) has 9GHz and 6GB and Host 3 (H3) has 6GHz and 6GB.

  • There are five powered-on virtual machines in the cluster with differing CPU and memory requirements. VM1 needs 2GHz of CPU resources and 1GB of memory, while VM2 needs 2GHz and 1GB, VM3 needs 1GHz and 2GB, VM4 needs 1GHz and 1GB, and VM5 needs 1GHz and 1GB.

  • The Host Failures Cluster Tolerates is set to one.

  1. Slot size is calculated by comparing both the CPU and memory requirements of the virtual machines and selecting the largest.

    The largest CPU requirement (shared by VM1 and VM2) is 2GHz, while the largest memory requirement (for VM3) is 2GB. Based on this, the slot size is 2GHz CPU and 2GB memory.

  2. Maximum number of slots that each host can support is determined.

    H1 can support four slots. H2 can support three slots (which is the smaller of 9GHz/2GHz and 6GB/2GB) and H3 can also support three slots.

  3. Current Failover Capacity is computed.

    The largest host is H1 and if it fails, six slots remain in the cluster, which is sufficient for all five of the powered-on virtual machines. If both H1 and H2 fail, only three slots remain, which is insufficient. Therefore, the Current Failover Capacity is one.

The cluster has one available slot (the six slots on H2 and H3 minus the five used slots).

In my previous Experts Exchange Articles, most have featured Basic and Intermediate VMware and Virtualisation Topics.


If you would like to read my Basic VMware articles, they are listed at the end of this article for your convenience.


Vsphere Web Client Address

This article will show you how to connect and complete some basic configuration of the VMware vSphere Hypervisor 6.7 on a computer. VMware vSphere Hypervisor 6.7 is also known as ESXi 6.7.


If you have missed the first article in the series, it's here:HOW TO: Install and Configure VMware vSphere Hypervisor 6.7 (ESXi 6.7)

1. Download Tools to Manage the ESXi Host Server


(Actually, there are no tools required now to manage ESXi 6.7!) ESXi 6.7 can now be managed by any web browser using the VMware Host Client, which is based on HTML5 technology. In this article, I'm using Google Chrome.



When the VMware vSphere Hypervisor (ESXi 6.7) server is fully BOOTED and started the above screen is displayed. This screen is called the Direct Console User Interface (DCUI). The majority of the management is performed remotely from another computer using a web browser. The VMware vSphere Client based on the programming language C#. is now deprecated, and not supported for use with managing and configuring a VMware vSphere Hypervisor (ESXi 6.7) host.


I'm not going to concentrate on using the VMware vSphere Client in this article or any later articles in this series, because it's about time, we get to grips with using the VMware Host (HTML5 Web) Client 6.7 and a web browser to configure our Hosts and Virtual Machines, as much as we moan, about how we do not like the Web Client.


You cannot manage or install virtual machines from the ESXi 6.7 server console; this must be completed remotely from another computer.
Make a note of the IP Address of the server which is displayed on the console, and using a web browser, browse to the web URL http://192.168.182.128. (This is the IP Address displayed on the console screen; your IP address will be different).
HOWEVER, it's recommended to use the FQDN of the host, so ensure your DNS is working correctly. Also, make sure you have created a DNS A Record for your ESXi host so that you can use its FQDN in your web browser.
The following screen will be displayed. Because VMware's SSL certificate has been 'self-signed' the warning is normal. Click Advanced to Proceed to manage the host. In this example, we are using Google Chrome.



After clicking continue, the login screen will be displayed:



Enter the default username root, and the password you have configured. The default username for an ESXi host is always root. From questions which have been posted to Experts Exchange there is always some confusion between direct access and management of an ESXi host, and connecting and managing via VMware vCenter Server.


2. Connecting to the VMware vSphere Hypervisor ESXi 6.7 server


When connecting for the first time to an ESXi 6.5 host, you will be asked to join the VMware's Customer Experience Improvement Program. (CEIP).



Select the Tick Box, and Select OK to continue.
You are now connected to the VMware vSphere Hypervisor ESXi 6.7 Server.




You will notice the ESXi host does not have persistent storage. To store virtual machines (often referred to as Guests or Virtual Machines (VMs), the VMs must be stored and reside on an ESXi host datastore. The VMware vSphere Hypervisor ESXi server has a compatible filing system called VMFS (similar to Microsoft Windows NT/2000/XP/2003/2008/2012/7/8, which has its own filing system called NTFS). There are three versions of VMFS: VMFS-3 for earlier versions of vSphere e.g. 3.x and 4.x, and VMFS-5 for vSphere 5.x and 6.0, and now VMFS-6 for 6.5/6.7.


3. Conducting a simple task using the VMware vSphere Client


In this step, we will complete a simple task using the VMware Host Client, this task is to Create a new VMFS datastore, so we can store VMs. This is the minimum configuration requirement for your ESXi host.
Select and Click Storage



Select New datastore to create a new datastore. (A new datastore is a virgin unformatted or partitioned disk or LUN. Do not use this option if the disk or LUN already has a datastore, which has been created by ESXi. e.g. it has VMFS on it!



At the following screen, select Create new VMFS datastore



followed by Next to continue
At the next screen select the actual Disk or LUN, pay special attention to the sizes shown. The size should match the size of the disk, LUN or array size you have created for your VMFS datastore, followed by Next to Continue. In this tutorial, we are going to select the 120GB Disk/LUN, the first entry in the list.


ANDY TIP:- Always start and create small disks or LUNs, they can easily be expanded in the future and it's more difficult to shrink a disk or LUN than increase it! In this tutorial series, we will later use this small datastore to host two virtual machines of 40GB each.



Enter the name for the datastore (do not use / * # ! @ (non-alpha numeric characters); it will accept them, but you will have issues later. The dash and underscore are okay.)


Client

The Geeks amongst you may have noticed that I'm using NVMe flash in this ESXi hypervisor! It is supported as a datastore.


Click Next to Continue



There are many different types of naming conventions. We like to use the name of the server followed by an underscore (_) local for local disk, iscsi for iscsi disk, nfs for nfs storage, fibre for fibre channel, a number to indicate disk or LUN id number, followed by VMFS type, e.g. 3, 5 or 6. For example: esx001_local1_vmfs6
Now click Next to Continue



The Current Disk Layout will be shown. If this is a used disk, it could show other partition types. (NTFS, FAT32, Linux, Swap, ext2, ext3) Click Next to Continue. This is a new disk in this tutorial, so a new partition will be created and used.
You have a choice of selecting VMFS-5 (ESXi 5.x and 6.0) or VMFS 6 (6.5 and 6.7 only). If all your Hosts will be 6.5/6.7, select VMFS 6, if you need them to be backward compatible with older hosts select VMFS-5.



Install Vsphere Web Client

Check the Summary screen for the datastore you are about to create and Click Finish to create the datastore.



Select yes, to erase the contents of the disk.




You are now ready to use your ESXi server.


Vsphere Web Client 5.5 Download


Congratulations you have successfully connected to the VMware vSphere Hypervisor 6.7 (ESXi 6.7) using the vSphere (HTML5 Web) Host Client 6.7, and created your first VMware VMFS-6 datastore ready to store Virtual Machines.


Basic VMware Articles Series:


These articles are also applicable to VMware vSphere Hypervisor ESXi 5.0, 5.5, 6.0.


These articles are applicable to VMware vSphere Hypervisor 6.5.

Vsphere Web Client Slot Size



Vsphere Web Client Download


Vsphere Web Client 6.7





What Is Vsphere Web Client


Vsphere Web Client 6.0 Download

If you found this tutorial helpful, please do click the Thumbs-Up icon below. This lets me know what is valuable for EE members and provides direction for future articles. Thank you very much! Regards, Andy