Is that your means for calculate bandwidth we had to just count witness components ?

For sure, because for 2-noder or stretched cluster you need to understand how many witness components should be placed on witness vm/node and after that count aggregate bandwidth (for that you should count 1138B sended to every witness component on witness-vm each 5 sec)

Objects and Components
Each object is composed of a set of components, determined by capabilities that are in use in the VM Storage Policy. For example, with Primary level of failures to tolerate set to 1, vSAN ensures that the protection components, such as replicas and witnesses, are placed on separate hosts in the vSAN cluster, where each replica is an object component. In addition, in the same policy, if the Number of disk stripes per object configured to two or more, vSAN also stripes the object across multiple capacity devices and each stripe is considered a component of the specified object. When needed, vSAN might also break large objects into multiple components.
A vSAN datastore contains the following object types:
VM Home Namespace
The virtual machine home directory where all virtual machine configuration files are stored, such as .vmx, log files, vmdks, and snapshot delta description files.
VMDK
A virtual machine disk or .vmdk file that stores the contents of the virtual machine's hard disk drive.
VM Swap Object
Created when a virtual machine is powered on.
Snapshot Delta VMDKs
Created when virtual machine snapshots are taken.
Memory object
Created when the snapshot memory option is selected when creating or suspending a virtual machine.

Objects and components

Exactly. Vsan Objects consist of vsan components. 😀

the truth is found can go drink beer

Thanks
Now a vm with ftt=1 and vmdk size=200 and stripe=1  due power on has 6 component + 3 witness thus 9 components is that correct?

Yes

But just to be clear - this is a minimum numbers. In real life it could have more components (snapshots, delta components, vmdk also could be stripped even with policy stripe=1 for balancing/capacity reasons, etc). But for rough estimates it is fine

Swap file is also component?

Swap is an object. Consist of 3 (2 data and witness) or more if ftt>1 (but ignoring striping policy) components.

By default due create FTT=1 we have 3 witness :
1- for vmdk
2- for swap
3- for home space

But now I change policy to FTT=1 with stripe=2
Now I have just two witness
1- for home space
2- for swap
Why there is not witness for vmdk ?

It's still there. It's an example -

This is my status . It is without witness why ?

Also change ftt=0 to ftt=1 with stripe=2 and this is my status and is not normal why happend this ?

Would you please help me about those issues?