create and drop tablespace

Hi experts.
I  created a tablspace successful on master  postgres# create tablespace portal_tbspc owner xxx location '/portaldata/postdata/portal_tbspc';CREATE TABLESPACE
but didn't see datafile exist in slave. 

Tried to drop the tablespace (and recreate it) #DROP TABLESPACE portal_tbspc;   and it hung for so long.
I tried to recreate the same tablspace name again and it error already exists... (I know that but don't know why it hung for so long when I dropped it)
create another tablespacce and still pause for more than 5 minutes, I cancelled the request and received:#create tablespace portal_tablespace location '/portaldata/postdata/portal_data';^CCancel request sentWARNING: canceling waiting for synchronous replication due to user requestDETAIL: The transaction has already committed locally, but might not have been replicated to the stanbyCREATE TABLESPACE
what cause the problem? Why the 1st creation is fine but can't drop? Second one is pausing for so long?  How can I resolve this issue?

Bach-Nga

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