vCenter HA?

[IvarHome]

Hi, how much exactly vCenter HA need memory? I readed from documentation that it needs 16GB memory. I dont believe this, because now I have vCenter with only 10GB memory and in reality it uses only 1.6GB active memory (ESXi monitoring utilization shows). And also, why witness needs the same amount of memory. So, this sounds bullshit. I have 2 more computers with 8 GB physical memory. I can set cluster VM more amount of memory than physical memory. Anyway it dont use them all. And witness? How much RAM I need exactly and how much for witness?......Or my question is - 16GB for VM or for ESXi? Im tired for searching internet. All articles are just like copy-paste "16GB" , but there is big difference is this requirement for VM or ESXi. And what happens when I have less.

[IRIX201110141]

Because VMware only supports the installation type of "small" and up and not the "tiny" one. A vCenter "small" have 4 CPUs and 16GB.

Regards,

Joerg

[IvarHome]

But what means 16GB? Is this also for witness computer? But what if I set 16GB, but actually in physical computer is 8GB RAM?

[IRIX201110141]

If you select the basic workflow the witness VM will be automaticly downsized to 1vCPU and 1GB vRAM. IIRC this is not happend if you select the adv. workflow.

Regards,

Joerg

[IvarHome]

Hi, how much exactly vCenter HA need memory? I readed from documentation that it needs 16GB memory. I dont believe this, because now I have vCenter with only 10GB memory and in reality it uses only 1.6GB active memory (ESXi monitoring utilization shows). And also, why witness needs the same amount of memory. So, this sounds bullshit. I have 2 more computers with 8 GB physical memory. I can set cluster VM more amount of memory than physical memory. Anyway it dont use them all. And witness? How much RAM I need exactly and how much for witness?......Or my question is - 16GB for VM or for ESXi? Im tired for searching internet. All articles are just like copy-paste "16GB" , but there is big difference is this requirement for VM or ESXi. And what happens when I have less.

[daphnissov]

vCHA needs the memory that the documentation says if you want it to work properly. Challenge it all you want. Call BS if you like. That's the official guidance. If you choose not to follow it, you do so at your own peril.

[IRIX201110141]

vCenter  HA is not supportet for a "tiny" vCenter setup. You need vCenter "small" or greater and for me it sounds logical that both members of a cluster need to have same ressources. This is the reason why it starts with 16GB and as already told you the witness takes 1GB.

Regards,

Joerg

[IvarHome]

I dont believe it takes 16GB. I can give it 16GB virtually, but I dont believe physical computer need 16GB.

[sk84]

You can give your VMs what you want and overbook the physical resources. This is one of the advantages of virtualization. But overbooking resources can be a beast that can bite you very quickly if you're not careful.

I can give it 16GB virtually, but I dont believe physical computer need 16GB.

I also think you didn't understand what Active Guest Memory means. These are only the active memory pages that were used in a certain time interval. It doesn't mean that they are the same memory pages as in the previous interval. And how much active guest memory your vCenter uses depends on the size of the infrastructure and the changes on virtual machines layer. If you only have 3 VMs running, it may be only a few GB of active guest memory. If your vCenter has to manage thousands of VMs and changes happen all the time, the active guest memory usage is way above that. But then you can't get along with an appliance size with 16 GB of configured memory.

[daphnissov]

I dont believe it takes 16GB. I can give it 16GB virtually, but I dont believe physical computer need 16GB.

Some people believe the Earth is flat. You're welcome to believe whatever you want.

[IvarHome]

But still the information is some insufficient. What means 16GB reguirement? Is this requirement for VM or for ESXi ram?

I have 6 ESXi hosts and about total 15 VM-s. In vCenter ESXi I have only vCenter VM.

[daphnissov]

What means 16GB reguirement? Is this requirement for VM or for ESXi ram?

The vCenter Server Appliance VM must be 16 GB in size (small) and the peer node must also be the same size.

[sk84]

The vCenter appliances are virtualized. So we're talking about requirements at the virtualization level. The VMs must therefore have at least 16 GB memory. But since a virtual machine needs underlying physical ressources and can't exist in a vacuum, you'd be well advised if that capacity can somehow be provided by the physical servers.

[IvarHome]

But for passive node it makes VM itself while setup, I dont set at all any value to VM memory.  So, I have right now for passive node empty ESXi with 8GB ram. Is setup able to initialize (copy passive node to that host) or it denies setup. When it can copy passive node to ESXi with 8GB ram, I can later increase passive VM ram to 16GB without problem. But if setup dont allow me to initialize, then I must set up nested ESXi, initialize HA and then move passive node from nested ESXi to physical ESXi............And how about active node. Do I need before vCenter HA setup increase vCenter VM ram from 10GB to 16GB (right now its 10GB)?

[sjesse · Accepted solution]

The passive and witness nodes are clones of your vcenter. If your vcenter isn't the size of a small, then you want to increase the memory and cpu to the correct size. Just connect to the host vcenter is on, shut it down and increase it to the 16gb and 4 vCPU thats needed. Then if you can do the basic ha setup vcenter will clone the vcsa for you and finish the setup , if not you  need to manually clone them when using the advanced setup.