How can I remove all metadata from an AVAMAR VIRTUAL EDITION ?

AVE's create data and meta areas on the disc and these are permanent. So if you accidentally created a dataset and sent the data to the ave you are stuck as when data or meta data is removed it can only be used for the same data again.

Once a stripe is created in the Avamar GSAN it exists forever and cannot be removed. 

If, for example, you accidentally sent backups to the Avamar GSAN, rather than to DataDomain, it would result in data stripes (which are relatively large, at 360MB) being created in the /dataxx partitions.

Deleting those backups would free up space within the data containers but the containers themselves will continue to exist and consume file system space which is no longer available for the creation of metadata containers.  The amount of data that can be backed up to DataDomain is therefore greatly reduced.

This is why Support advised that the AVE will need to be reinstalled. 

How absurd is that...

is there a way to make sure NO BACKUP DATA AT ALL is stored on the Avamar ?

is there a way to limit the possibility ?

reinstalling the backup server (Avamar virtual) is a time consuming operation...

There is a way to lock backups to data domain.  Instructions how to configure this is in partner\EMC pro services documentation.

Still absurd... but this is the setting you are referring to, I guess:

There are two mcserver.xml parameters that control whether backups are forced to go to Data Domain or not:

dd_only_mode = ALL | SUPPORTED | DATASET

  ALL – all backups not in dd_only_exclusion list go to DD; those that are not supported will fail

  SUPPORTED – all backups that are supported by DD go to DD except for those in exclusion list

  DATASET – controlled by dataset – default value

dd_only_exlusion = plugin ID’s

  All plugins in this list sent to GSAN in dd_only_mode=ALL or SUPPORTED.

Generally speaking, these parameters are set at install or upgrade time. Under normal circumstances, these settings should only be changed from a less restrictive setting to a more restrictive setting (from DATASET to SUPPORTED, from DATASET to ALL, etc.). In particular, Avamar / Data Domain integrated systems with high metadata capacity often have the dd_only_mode set to a more restrictive value (SUPPORTED or ALL) by the RCM team during upgrades and this must not be undone because it is likely to cause metadata capacity issues on the Avamar system.