I notices when I use @ElementCollection the entity will be persisted without the list and the list will be set afterwards with an extra update.

Due to the fact the list is embedded I would expect it to be saved within the first insert.

@Entity
@Table(name = "logs")
public class LogEntry {
...
@ElementCollection(fetch = FetchType.EAGER)
private List<String> subsystems;

Log Output:
save: ogm-eval.logs { "_id" : "eventId" , "logTimestamp" : "2016/01/21 11:56:04:686 +0100" , "systemData" :

, "version" : 0}
<- note subsystems omitted!

update: ogm-eval.logs

{ "$set" : { "subsystems" : [ "PAYMENT" , "DEBIT"]}}
<- this update comes afterwards

So for one insert two queries are generated which is a performance concern!

Code snipped is straightforward forward:

LogEntry entry = new LogEntry();
entry.setSubsystems(Arrays.asList("PAYMENT", "DEBIT"));
em.persist(entry);