Can we take instant snapshots on a set (within a namespace)?
Aerospike support incremental backups which can be taken at either the set or namespace level.
See the asbackup documentation.
Specifically these options may of interest: --namespace, --set, and -a.
“Instant snapshot” no. You can’t just take a full backup of all the data instantly. If your block storage device supports this, then you can take a snapshot of the block device - but even if you’re using asbackup or blockdev snapshots/isos then you still have the potential for data to be changed while its running. For something to be a true ‘instant’-like and consistent snapshot, you’d probably want to shut off the entire cluster and take images/copies of the drives. Totally depends on what your goal is here.