pxc start senond node report error

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when xtrabackup errror

141216 14:16:44  innobackupex: Connecting to MySQL server with DSN 'dbi:mysql:;mysql_read_default_file=/export/servers/mysql/etc/my.cnf;mysql_read_default_group=xtrabackup;mysql_socket=xxxx/mysql.sock' as 'sst'  (using password: YES).

141216 14:16:44  innobackupex: Connected to MySQL server

141216 14:16:44  innobackupex: Executing a version check against the server...

141216 14:16:44  innobackupex: Done.

141216 14:16:44  innobackupex: Starting the backup operation

IMPORTANT: Please check that the backup run completes successfully.

           At the end of a successful backup run innobackupex

           prints "completed OK!".

innobackupex:  Using server version 5.6.20-68.0-25.7-log

innobackupex: Created backup directory /tmp

141216 14:16:44  innobackupex: Starting ibbackup with command: xtrabackup  --defaults-file="/export/servers/mysql/etc/my.cnf"  --defaults-group="mysqld" --backup --suspend-at-end --target-dir=/tmp --tmpdir=/tmp --extra-lsndir='/tmp' --stream=tar

innobackupex: Waiting for ibbackup (pid=13334) to suspend

innobackupex: Suspend file '/tmp/xtrabackup_suspended_2'

xtrabackup version 2.2.6 based on MySQL server 5.6.21 Linux (x86_64) (revision id: )

xtrabackup: uses posix_fadvise().

xtrabackup: cd to /export/data/mysql/data

xtrabackup: open files limit requested 65535, set to 65536

xtrabackup: using the following InnoDB configuration:

xtrabackup:   innodb_data_home_dir = /export/data/mysql/data

xtrabackup:   innodb_data_file_path = ibdata1:1G;ibdata2:1G:autoextend

xtrabackup:   innodb_log_group_home_dir = /export/data/mysql/data

xtrabackup:   innodb_log_files_in_group = 3

xtrabackup:   innodb_log_file_size = 536870912

xtrabackup: using O_DIRECT

>> log scanned up to (1627462)

xtrabackup: Generating a list of tablespaces

[01] Streaming /export/data/mysql/data/ibdata1

>> log scanned up to (1627462)

>> log scanned up to (1627462)

>> log scanned up to (1627462)

>> log scanned up to (1627462)

.........

xtrabackup: Error writing file 'UNOPENED' (Errcode: 32 - Broken pipe)

archive_write_data() failed: (Empty error message) (errno = 0)

[01] xtrabackup: Error: xtrabackup_copy_datafile() failed.

[01] xtrabackup: Error: failed to copy datafile.

innobackupex: got a fatal error with the following stacktrace: at /usr/bin/innobackupex line 2694

        main::wait_for_ibbackup_file_create('/tmp/xtrabackup_suspended_2') called at /usr/bin/innobackupex line 2714

        main::wait_for_ibbackup_suspend('/tmp/xtrabackup_suspended_2') called at /usr/bin/innobackupex line 1968

        main::backup() called at /usr/bin/innobackupex line 1592

innobackupex: Error: The xtrabackup child process has died at /usr/bin/innobackupex line 2694.