| Setting | Old | New | Notes |
| back_log | 50 | 50 + ( max_connections / 5 ) capped at 900 | |
| binlog_checksum | NONE | CRC32 | New variable in 5.6. 5.5 doesn't accept the checksums. Use NONE if you want to read binlog with 5.5 or on master if have replication slaves using 5.5. |
| binlog-row-event-max-size | 1k | 8k | no binlog_row_event_max_size variable, just the option form. |
| flush_time | 1800 | Windows changes from 1800 to 0 | Was already 0 on other platforms |
| host_cache_size | 128 | 128 + 1 for each of the first 500 max_connections + 1 for every 20 max_connections over 500, capped at 2000 | New variable in 5.6 |
| innodb_autoextend_increment | 8 | 64 | 64 is 64 megabytes |
| innodb_buffer_pool_instances | 0 | 8. On 32 bit Windows only, if innodb_buffer_pool_size is greater than 1300M, default is innodb_buffer_pool_size / 128M | |
| innodb_concurrency_tickets | 500 | 5000 | |
| innodb_file_per_table | 0 | 1 | |
| innodb_log_file_size | 5M | 48M | InnoDB will change size to match my.cnf value. Also see innodb_log_compressed_pages and binlog_row_image |
| innodb_old_blocks_time | 0 | 1000 | 1 second |
| innodb_open_files | 300 | 300. If innodb_file_per_table is ON, higher of table_open_cache or 300 | |
| innodb_purge_batch_size | 20 | 300 | |
| innodb_purge_threads | 0 | 1 | |
| innodb_stats_on_metadata | on | off | |
| join_buffer_size | 128k | 256k | |
| max_allowed_packet | 1M | 4M | |
| max_connect_errors | 10 | 100 | |
| open_files_limit | 0 | 5000 | See Note 1 |
| query_cache_size | 0 | 1M | |
| query_cache_type | ON/1 | OFF/0 | |
| sort_buffer_size | 2M | 256k | |
| sql_mode | none | NO_ENGINE_SUBSTITUTION | See later post about default my.cnf for STRICT_TRANS_TABLES |
| sync_master_info | 0 | 10000 | Recommend: master_info_repository=table |
| sync_relay_log | 0 | 10000 | |
| sync_relay_log_info | 0 | 10000 | Recommend: relay_log_info_repository=table. Also see Replication Relay and Status Logs |
| table_definition_cache | 400 | 400 + table_open_cache / 2, capped at 2000 | |
| table_open_cache | 400 | 2000 | Also see table_open_cache_instances |
| thread_cache_size | 0 | 8 + max_connections/100, capped at 100 |
轉自：
https://blogs.oracle.com/supportingmysql/entry/server_defaults_changes_in_mysql