user1032531 asked:
I installed two new CentOS 6.4 installations; one on an i686 VPS and the other on a physical x86_64 desktop, installed MySQL 5.1.69 on both using yum install mysql-server using CentOS’s repository, and made no other changes. SHOW VARIABLES; are identical on both except for the following. Why are they different? Does one have “better” values than another? If so, why is one better than the other.
+---------------------------+-----------------------+-------------------------+
| | i386 | x86_64 |
+---------------------------+-----------------------+-------------------------+
| max_binlog_cache_size | 4294963200 | 18446744073709500000 |
| max_seeks_for_key | 4294967295 | 18446744073709500000 |
| max_write_lock_count | 4294967295 | 18446744073709500000 |
| myisam_max_sort_file_size | 2146435072 | 9223372036853720000 |
| myisam_mmap_size | 4294967295 | 18446744073709500000 |
| plugin_dir | /usr/lib/mysql/plugin | /usr/lib64/mysql/plugin |
+---------------------------+-----------------------+-------------------------+
My answer:
One architecture is 32-bit and the other is 64-bit. Those values correspond more or less exactly to the maximum unsigned and signed 32-bit and 64-bit vaules.
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