Taking backup on Zenoss CLI failed. Using CentOS 6.5

[zenoss@ ~]$ zenbackup --file=/opt/zenoss/backups
INFO:zenbackup:Getting ZEP dbname, user, password, port from configuration files.
INFO:CoreBackup:Backing up the events database.
INFO:CoreBackup:Backing up event indexes.
INFO:CoreBackup:Backing up event indexes completed.
INFO:zenbackup:Backup of events database completed in 7 minutes.
INFO:CoreBackup:Backing up config files.
INFO:CoreBackup:Backup of config files completed.
INFO:CoreBackup:Backing up the ZODB.
INFO:zenbackup:Backup of ZODB database completed in 25 seconds.
INFO:CoreBackup:Backing up ZenPacks.
INFO:CoreBackup:Backup of ZenPacks completed.
INFO:CoreBackup:Backing up bin dir.
INFO:CoreBackup:Backup of bin completed.
2015-04-15 15:16:18,339 INFO CoreBackup: Backing up ZenPack contents.
2015-04-15 15:16:18,351 INFO CoreBackup: Backup of ZenPack contents complete.
2015-04-15 15:16:18,351 INFO zenbackup: Backup of ZenPacks completed in 2 seconds.
2015-04-15 15:16:18,352 INFO CoreBackup: Backing up performance data (RRDs).
2015-04-15 15:18:17,152 WARNING zenbackupbase: tar: /tmp/tmpTlz9oR/zenbackup/perf.tar: Wrote only 2048 of 10240 bytes
tar: Error is not recoverable: exiting now

2015-04-15 15:18:17,153 INFO zenbackup: Packaging backup file.
2015-04-15 15:18:17,175 WARNING zenbackupbase: tar (child): /opt/zenoss/backups: Cannot open: Is a directory
tar (child): Error is not recoverable: exiting now
tar: /opt/zenoss/backups: Wrote only 2048 of 10240 bytes
tar: Error is not recoverable: exiting now

2015-04-15 15:18:17,176 INFO zenbackup: Cleaning up staging directory /tmp/tmpTlz9oR
2015-04-15 15:18:17,794 CRITICAL zenbackup: 'Performance Data backup failed.'
2015-04-15 15:18:17,794 CRITICAL zenbackup: 'Backup packaging failed.'