Hello Philippe,
I have tested this procedure in vSAN HOL 1808, by configuring a 3-node vSAN cluster, migrating 'core-A' VM to this cluster and vsandatastore, adding a few disks with different SPs to this VM and cloning this VM to put more data on the cluster. Then adding 3 other nodes to the vSphere cluster(hosts 04-06 require their vSAN vmks added/IP changed + Default gateway changed) then configuring the Fault Domains and Witness and creating disk-groups on hosts 04-06.
http://labs.hol.vmware.com/HOL/catalogs/lab/3651
As soon as stretched-cluster was configured all VM Objects were of state 'Reduced Availability with no rebuild' but remained accessible through-out (checked via console of running VMs), these then started automatically resyncing all Objects as soon as disk-groups were configured on the new hosts. Thus I don't think you will have the choice of selectively resyncing some VMs/Objects at a time by re-applying Storage Policies (but do also bear in mind that HOL is nested nested and can have quirky behaviour )
The reliable and safe method of throttling resync in 6.2 is to lower the IO to resyncing components from the default of 50, anywhere down to 1, e.g.:
#vsish -e set /vmkModules/vsan/dom/MaxNumResyncCopyInFlight 1
This needs to be applied to all hosts and will of course slow down the resync.
Obviously there is only a need to do this if the additional load of the resync is causing unacceptable latency for production VMs.
You could start the resync with this lowered to 1 on all hosts and gradually increase while periodically checking that VM latency is acceptable.
"Just to clarify. In 6.2 throttle resync was "expanded" (in the background). This can be controlled by advanced commands such as:
- esxcfg-advcfg -s <x> /VSAN/DomCompResyncThrottle
- Vsish –e set /vmkModules/vsan/dom/compSchedulers/<component_id>ResyncIopsLimit 1000"
I am unsure of the safety of using either of those pre-6.6, I know that 'pausing' resync through similar means could cause mass-PSODs, can't recall if throttling could have the same effect.
Also, in ResyncIopsLimit vsish command those are NOT component UUIDs being referenced, they are cmmds UUIDs referencing the cache-tier SSDs of the host that command is being run on.
Bob