MySQL slave database won't start
Unknown system variable 'binlog_checksum'


That's because your master is running MySQL 5.5 (or earlier), and the slave is running MySQL 5.6. The binlog_checksum global variable was introduced in 5.6, and the slave is trying to find out if that feature is enabled on the master. But the variable doesn't exist on your master. This shouldn't cause any data loss, and the warning will go away once you upgrade your master.


  Client requested master to start replication from impossible position


Sounds like your master crashed before it could write a final "Rotate to next binlog" event at the end of a binlog file. So the slave doesn't know to advance to the next binlog.

You can manually change the slave to read from the next binlog:

mysql&gt; STOP SLAVE;
mysql&gt; CHANGE MASTER TO MASTER_LOG_FILE='mysqliv-bin.000143', MASTER_LOG_POS=4;
mysql&gt; START SLAVE;


But first, double-check that mysqliv-bin.000143 exists on the master with SHOW BINARY LOGS.

The following blog explains in more detail:
http://www.skysql.com/blogs/adam-donnison/client-requested-master-start-replication-impossible-position