MYSQL DATABASE BACKUP Currently my backup strategy invloves :-

1)I have one master server and two slaves (Data approximately 700 GBs and tables are of mixed innodb and myisam).

2)I take weekly and monthly backup from slave through mysqldump.

3)In case of slave failure ,will copy data from another slave.

My question is  should i change this backup strategy ??
Should i use percona xtrabackup and if yes why ??
700GB is too much for mysqldump. Restore will take too much time (but I would measure to know numbers). XtraBackup will be faster.

Taking backup from a slave is OK, but you have to make sure the master and slave are in sync. Use pt-table-checksum to verify that.

And what is missing in your strategy is backups verification. If you don't verify backups you don't have backups.