replication timeout in pg_basebackup

Our environment: Postgres version 9.2.2 running on CentOS 6.4

Our backups using pg_basebackup are frequently failing with following error

"pg_basebackup: could not send feedback packet: server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request."

We are invoking pg_basebackup with these arguments : pg_basebackup -D backup_dir -X stream -l backup_dir

In postgres logs we see this log message "terminating walsender process due to replication timeout".

Our replication timeout is default 60 seconds. If we increase the replication time to say 180 seconds, we see better results but backups still fail occasionally.

Running strace on pg_basebackup process, we see that the fsync() call takes significant time and could be responsible for causing this timeout in postgres.

Has anybody else run into the same issue? Is there a way to run pg_basebackup without fsync() ?