Hello vmb01,
"the question is: if a virtual machine writes new data, this new data are replicated between the two hosts?"
Well it depends what is still available after loss of single component.
1. If both data-components are still available (e.g. lost witness-component) it will write changes to both.
2. If only one data-component + witness-component is available (e.g. lost an R1 data-component) it can only update the available component and thus when/if the absent component comes back it is stale and has to be resynced the delta of changes that occurred during its absence.
"know that if I have more than 2 host the vsan waits 60 minutes and after begin to creare a new copy of data... but if I have just 2 hosts, what happens?"
Nothing happens - it won't try to rebuild the absent components as it has no where to put them while also satisfying the FTT e.g. rebuilding the 2nd data-component on the same node wouldn't be beneficial for availability.
If you only have 2/3 Fault Domains (nodes here) available for placement of components then creation of new Objects (e.g. vmdk) will fail unless they have ForceProvisioning set on them such as how .vswp Objects have by default (so that you can still power-on VMs with only 2 of 3 nodes available) - this basically aims to create as many components as currently possible e.g. data + witness (and rebuilds the remainder when enough Fault Domains become available).
Bob
