MySQL Tuning and Optimization

MySQL is a powerful open-source database. With more and more database driven applications, people have been pushing MySQL to its limits. Here are some tips for tuning and optimizing your MySQL install. Some tips are specific to the environment they are installed on, but the concepts are universal.

MySQL Server Hardware and OS Tuning:
1. Have enough physical memory to load your entire InnoDB file into memory – InnoDB is much faster when the file can be accessed in memory rather than from disk.
2. Avoid Swap at all costs – swapping is reading from disk, its slow.
3. Use Battery-Backed RAM.
4. Use an advanced RAID – preferably RAID10 or higher.
5. Avoid RAID5 – the checksum needed to ensure integrity is costly.
6. Separate your OS and data partitions, not just logically, but physically – costly OS writes and reads will impact your database performance.
7. Put your mysql temp space and replication logs on a separate partition than your data – background writes will impact your database when it goes to write/read from disk.
8. More disks equals more speed.
9. Faster disks are better.
10. Use SAS over SATA.
11. Smaller disks are faster than larger disks, especially in RAID configs.
12. Use Battery-Backed Cache RAID controllers.
13. Avoid software raids.
14. Consider using Solid State IO Cards (not disk drives) for your data partition – these cards can sustain over 2GB/s writes for almost any amount of data.
15. On Linux set your swappiness value to 0 – no reason to cache files on a database server, this is more of a web server or desktop advantage.
16. Mount filesystem with noatime and nodirtime if available – no reason to update database file modification times for access.
17. Use XFS filesystem – a faster, smaller filesystem than ext3 and has more options for journaling, also ext3 has been shown to have double buffering issues with MySQL.
18. Tune your XFS filesystem log and buffer variables – for maximum performance benchmark.
19. On Linux systems, use NOOP or DEADLINE IO scheduler – the CFQ and ANTICIPATORY scheduler have been shown to be slow vs NOOP and DEADLINE scheduler.
20. Use a 64-bit OS – more memory addressable and usable to MySQL.
21. Remove unused packages and daemons from servers – less resource stealing.
22. Put your host that use MySQL and your MySQL host in a hosts file – no dns lookups.
23. Never force kill a MySQL process – you will corrupt your database and be running for the backups.
24. Dedicate your server to MySQL – background processes and other services can steal from the db cpu time.

MySQL Configuration:
25. Use innodb_flush_method=O_DIRECT to avoid a double buffer when writing.
26. Avoid O_DIRECT and EXT3 filesystem – you will serialize all your writes.
27. Allocate enough innodb_buffer_pool_size to load your entire InnoDB file into memory – less reads from disk.
28. Do not make innodb_log_file_size too big, with faster and more disks – flushing more often is good and lowers the recovery time during crashes.
29. Do not mix innodb_thread_concurrency and thread_concurrency variables – these two values are not compatible.
30. Allocate a minimal amount for max_connections – too many connections can use up your RAM and lock up your MySQL server.
31. Keep thread_cache at a relatively high number, about 16 – to prevent slowness when opening connections.
32. Use skip-name-resolve – to remove dns lookups.
33. Use query cache if your queries are repetitive and your data does not change often – however using query cache on data that changes often will give you a performance hit.
34. Increase temp_table_size – to prevent disk writes.
35. Increase max_heap_table_size – to prevent disk writes.
36. Do not set your sort_buffer_size too high – this is per connection and can use up memory fast.
37. Monitor key_read_requests and key_reads to determine your key_buffer size – the key read requests should be higher than your key_reads, otherwise you are not efficiently using your key_buffer.
38. Set innodb_flush_log_at_trx_commit = 0 will improve performance, but leaving it to default (1), you will ensure data integrity, you will also ensure replication is not lagging
39. Have a test environment where you can test your configs and restart often, without affecting production.

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