Some of those files are used to restore the backup or to make incremental backups for example.

xtrabackup_checkpoints will store the LSN range of this backups. It is used for incremental backups..
xtrabackup_binlog_info will contain the the bin log file and position when you made the backup. It will be useful if you want to create slaves from this backup
xtrabackup_binlog_pos_innodb if the same as xtrabackup_binlog_info but only valid if you only have XtraDB of InnoDB tables.
xtrabackup_binary xtrabackup used to make the backup.
xtrabackup_logfile used to restore your backup.

I don't understand why you might want to remove those files from a backup.. but not.. this is not recommended.

Bye

Hi,

Thanks for reply.

Basically I've restored slave server with Xtrabackup script. I'm not planning to use it any more on these server so I though I'll clean out these files from MySQL data directory.

Regards