Snapshot from Vmware or « snapshot from NetApp thru consistent snapshot »? The snapshot from Vmware is stable but manually you have to create it but if you want to schedule then use the SMVI which will quiesce and take the snapshot which is stable, consistent and doesn't disrupt any services.
Snapshot consistent / non consistent, what do we use? VSS or Vmware tools ? The SMVI uses the VSS and it is stable. Don't use Vmware tools which is cumbersome process.
If consistent, is it OK for all application ? Can we be 100% sure that an application will starts without corrupt data? (SQL/Oracle database for exemple ) The best SMVI for VM level but application level suggested is Snapmanager for SQL or Oracle.
Snapshot of the memory, may the VM hang? No
If we have « independent persistent » HDD and if Vmware can't snapshot it, will netapp SMVI fail or may it succeed? SMVI will fail too.
Are there impacts if Storage DRS is used in Vmware ? obviously depending upon the DRS setup.
IF I would like to snapshot a VM on a datastore and if this VM has another HDD VMDK on another VMFS, will it succeed or not? yes obviously no problem
Agumadavalli provided some good answers but I thought I would expand on them a little;
Is there some best practices for backup and restore (VMFS size or type, VM, when to do them, impacts...)
This depends a little on the VMware snapshot option. In VSC Backup and recovery you can do a backup with or without the use of VMware Snapshots (more on that below) If you opt to do a backup without VMware snapshots then there is zero impact and you can do them whenever you want with as many VMs as you want. If you are using the VM snapshots you should limit the backups to a low utilization period for the ESX hosts and limit the number of datastores you are backing up.
2. Snapshots :
Snapshot from Vmware or « snapshot from NetApp thru consistent snapshot »? I'm not sure what you are asking here but I think it may be answered below.
Snapshot consistent / non consistent, what do we use? VSS or Vmware tools ? When you create the VSC backup job you can choose to use VMware snapshots or not. If you chose not to the VMware is what is known to be "crash consistent" That is no application quiecing was done. If you leverage the VMware snapshots, then VMware will create a VMware snapshot for the sole purpose of activating a VSS writer in the VM to try to quiece any VSS compatible application. This doesn't however rotate logs or verify the application data. My personal opinion is that the VSC backup is perfect as an image level backup not transactional VM. VMs with transactional or complex applications should have an application specific agent in them IE SnapCreator or SnapManager. Therefore the remaining VMs most likely do not benefit from the VMware snapshot and it can not be used. I personally recommend not using the VMware snapshot option and then leveraging SnapManager, SnapCreator or a traditional agent for transactional VMs.
If consistent, is it OK for all application ? Can we be 100% sure that an application will starts without corrupt data? (SQL/Oracle database for exemple ) (See above)
Snapshot of the memory, may the VM hang? VSC does not snapshot the memory of the VM.
If we have « independent persistent » HDD and if Vmware can't snapshot it, will netapp SMVI fail or may it succeed? SMVI/VSC can still back these up as long as the VMWare snapshot option is turned off.
Are there impacts if Storage DRS is used in Vmware ? Yes, This can be a tricky one. If you build your protection policies at the datastore level, which is my recommendation then the VM can move datastores and will be protected by the policy on the new datastore. However, VSC will only show the backups for that VM since it was placed in the new datastore. The older backups are still there on the old datastore but you would have know about them. We recommend Storage DRS is set to initial placement only then any other moves would be manual so this can be tracked.
IF I would like to snapshot a VM on a datastore and if this VM has another HDD VMDK on another VMFS, will it succeed or not? The default behavior of VSC/SMVI is that both datastores will be backedup at the same moment. You can however chosse to exclude one or the other datastore.
Is there a risk if ther is already some vmware snapshot for a VM? will they be shrink? No, VMware snapshots will always grow, VSC and SMVI can however work with VMs that have existing VMware snapshots but the hope is, with VSC the need for these other snapshot is reduced and ideally eliminated. VMware Snapshots are more of a redo log that queues IO till they are deleted, there can be a significant performance impact at that time so they should not be left for long periods of time.
If a snapshot fails, does netapp try another one? If a VMware snapshot fails the NetApp VSC/SMVI backup will still suceed but with warning since that VM may not have had it VMware snapshot created or deleted properly. If you use ANY tool that automatically creates VMware snapshots you should check for orphaned snapshots daily as often VMware snapshots do not delete properly with the API. NetApp has a free tool for this call CVMS. Just seach these communities for it.