Vsphere 5.5 ha slot size
This has always been a hot topic, HA and Slot sizes/Admission Control. One of the most extensive (Non-VMware) articles is by Chad Sakac aka Virtual Geek, but of. Learn what a slot is, how it is calculated, and how it affects your vSphere HA Admission Control. VMware HA Slot is the default admission control option prior to vSphere Slot Size is defined as the memory and CPU resources that satisfy the reservation.
Understanding VMware Slot Sizes
Although this sounds great admission control rules the host out with the most slots as it takes the worst case scenario into account. This results in 50 slots for esx01, esx02, esx03 and esx Therefore, the Current Failover Capacity is one. VM24 has a 4GB reservation set. What are our options? To avoid not being able to power on the VM with high reservations these VM will take up multiple slots. One thing worth mentioning, as Chad stated with vCenter 2.
HA and Slot sizes
What is a Slot? To begin this post, we need to understand what a slot is. Slot size is an important concept because it affects admission control.
A VMware ESXi cluster needs a way to determine how many resources need to be available in the event of a host failure. This slot calculation gives the cluster a way to reserve the right amount of resources. How are Slots Sized?
The slot has two parts, the CPU component and the memory component. Each of them has its own calculation. There are different sized VMs, but none of them have a reservation. Doing a quick calculation we can determine that slots are available on each host. So therefore we could safely start machines on these ESXi hosts, have one fail, and have the other host start all of them.
That would be a great consolidation ratio. Problem Scenario What if you have a single large VM with a reservation, but the rest of the virtual machines are relatively small. What are our options? Option 2 — We can manually configure the slot size on the cluster. Note that if you do this, some of your VMs will require multiple slots to run. For instance the large VM we used in our example might take more than 1 slot depending on what size you make it.
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One of the most extensive Non-VMware articles is by Chad Sakac aka Virtual Geek, but of course since then a couple of things has changed. Slot sizes Lets start with the basics. What is a slot? 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. In other words a slot size is the worst case CPU and Memory reservation scenario in a cluster. Now how does HA calculate how many slots are available per host?
Of course we need to know what the slot size for memory and CPU is first. Then we divide the total available CPU resources of a host by the CPU slot size and the total available Memory Resources of a host by the memory slot size. This leaves us with a slot size for both memory and CPU. The most restrictive number is the amount of slots for this host. If you have 25 CPU slots but only 5 memory slots the amount of available slots for this host will be 5.
As you can see this can lead to very conservative consolidation ratios. If you have just one VM with a really high reservation you can set the following advanced settings to lower the slot size being used during these calculations: To avoid not being able to power on the VM with high reservations these VM will take up multiple slots.
Keep in mind that when you are low on resources this could mean that you are not able to power-on this high reservation VM as resources are fragmented throughout the cluster instead of located on a single host. Now what happens if you set the number of allowed host failures to 1? The host with the most slots will be taken out of the equation. If you have 8 hosts with 90 slots in total but 7 hosts each have 10 slots and one host 20 this single host will not be taken into account.
And of course if you set it to 2 the next host that will be taken out of the equation is the host with the second most slots and so on. One thing worth mentioning, as Chad stated with vCenter 2. This led to a very conservative and restrictive admission control. This behavior has been modified with vCenter 2.
Those algorithms are proprietary to individual suppliers. Each one uses their own algorithms and there is no defined standard for them. Even if the Common Interface has been created to resolve cryptography issues, it can have other functions using other types of modules such as Web Browser , iDTV Interactive Television , and so forth. Conditional-access module CAM [ edit ] Main article: The CAM often contains a smart-card reader.
According to the Common Interface scheme: A small device, not working by itself, designed to run specialized tasks in association with a host; for example, a conditional access sub system, an electronic program guide application module, or to provide resources required by an application but not provided directly by the host. The specification only defines two aspects, two logical interfaces to be included on the same physical interface.
The link and physical layers are defined in this specification and the higher layers are defined in the MPEG-2 specifications.
The second interface, the command interface, carries commands between the host receiver and the module. The specification does not define the operation or functionality of a conditional access system application on the module. The applications that may be performed by a module communicating across the interface are not limited to conditional access or to those described in this specification. More than one module may be supported concurrently. By reducing the widths of the address and data busses it has been possible to include a bi-directional parallel transport stream interface.
Command Interface[ edit ] In addition there is a command interface for communication between the host and module.