Persistence with ruby sdk. Is it really persist if the disk write queue growing?

Hello.
I’m doing some load testing on a couchbase server 2.2 .
I’m doing set commands in this way:

client.set(key, value, :observe => {:persisted => 1})

In the client web console I can see 15000 ops per second but I can also see that the disk write queue is increasing.
Am I doing something wrong? It seems that the command doesn’t wait for the document to persist to disk.

Thanks

Thanks, I will investigate it

OK. No need to investigate.
I was using the async method.

Thank you
@avsej