LP #680927: xtrabackup --prepare to create logfile fails: innodb_init(): Error occured.

**Reported in Launchpad by Kenny Gryp last update 13-04-2011 14:08:55

If you set the innodb_doublewrite_file option, xtrabackup fails to --prepare the 2nd time:

MySQL version: 5.1.51-rel11.5-log
XtraBackup version: Ver 1.4 Rev 193 for 5.1.47 unknown-linux-gnu (x86_64)

xtrabackup Ver 1.4 Rev 193 for 5.1.47 unknown-linux-gnu (x86_64)
xtrabackup: cd to /home/gryp/xtrabackup/tracx/2010-11-24_14-11-49/
xtrabackup: This target seems to be already prepared.
xtrabackup: notice: xtrabackup_logfile was already used to '--prepare'.
xtrabackup: Temporary instance for recovery is set as followings.
xtrabackup: innodb_data_home_dir = ./
xtrabackup: innodb_data_file_path = ibdata1:10M:autoextend
xtrabackup: innodb_log_group_home_dir = ./
xtrabackup: innodb_log_files_in_group = 2
xtrabackup: innodb_log_file_size = 5242880
xtrabackup: Starting InnoDB instance for recovery.
xtrabackup: Using 104857600 bytes for buffer pool (set by --use-memory parameter)
InnoDB: The InnoDB memory heap is disabled
InnoDB: Mutexes and rw_locks use GCC atomic builtins
InnoDB: Compressed tables use zlib 1.2.3
InnoDB: Warning: innodb_file_io_threads is deprecated. Please use innodb_read_io_threads and innodb_write_io_threads instead
InnoDB: Notice: innodb_doublewrite_file is specified.
InnoDB: This is for expert only. Don't use if you don't understand what is it 'WELL'.
InnoDB: ### Don't specify older file than the last checkpoint ###
InnoDB: otherwise the older doublewrite buffer will break your data during recovery!
101124 14:14:49 InnoDB: Log file ./ib_logfile0 did not exist: new to be created
InnoDB: Setting log file ./ib_logfile0 size to 5 MB
InnoDB: Database physically writes the file full: wait...
101124 14:14:49 InnoDB: Log file ./ib_logfile1 did not exist: new to be created
InnoDB: Setting log file ./ib_logfile1 size to 5 MB
InnoDB: Database physically writes the file full: wait...
InnoDB: Cannot initialize created log files because
InnoDB: data files were not in sync with each other
InnoDB: or the data files are corrupt.
xtrabackup: innodb_init(): Error occured.

See attachment for more output.