innobackupex restore incremental backup failed ?

MySQL & MariaDB Percona XtraBackup
1

Hello ,Everyone
ask a restore question ?

I used mysql 5.6.14

  1. Full backup (normal) , backup full path : /home/backup/2014-04-01_17-00-15/
    innobackupex --defaults-file=/home/mysql/my.cnf --user=root --password=xxxxxx --socket=/home/mysqldata/data/mysql.sock /home/backup

  2. first incremental backup (normal) , backup path: /home/backup/2014-04-01_17-03-35
    innobackupex --defaults-file=/home/mysql/my.cnf --user=root --password=xxxxxx --socket=/home/mysqldata/data/mysql.sock --incremental /home/backup --incremental-basedir /home/backup/2014-04-01_17-00-15/

/home/backup/2014-04-01_17-12-01/
innobackupex --defaults-file=/home/mysql/my.cnf --user=root --password=xxxxxx --socket=/home/mysqldata/data/mysql.sock --incremental /home/backup --incremental-basedir /home/backup/2014-04-01_17-03-35

– 1. restore full backup ( normal)
innobackupex --defaults-file=/home/mysql/my.cnf --user=root --password=xxxxxx --socket=/home/mysqldata/data/mysql.sock --apply-log /home/backup/2014-04-01_17-00-15/

– 2. restore first incremental (normal)
innobackupex --defaults-file=/home/mysql/my.cnf --user=root --password=xxxxxx --socket=/home/mysqldata/data/mysql.sock --apply-log --redo-only /home/backup/2014-04-01_17-00-15/ --incremental-dir /home/backup/2014-04-01_17-03-35/

– 3. restore second incremental ( failed)
innobackupex --defaults-file=/home/mysql/my.cnf --user=root --password=xxxxxx --socket=/home/mysqldata/data/mysql.sock --apply-log /home/backup/2014-04-01_17-00-15/ --incremental-dir /home/backup/2014-04-01_17-12-01/

Error : unable open undo tablespace ./undo001

remak:

after set separately undo tablespace, execute last incremental restore , display error above.

if not set undo tablespace , restore normal.