… key cache hit ratio should be very high, ideally above 99.9%” or “if your key cache hit ratio is low, your key_buffer_size is…: you should care about the key cache hit ratio. Bad advice #2: you should set your key_buffer_size according to this ratio. Tuning… to do a Key_read as a Key_read_request, what use would the key buffer be anyway? Let’s trust MyISAM‘s creators…
Post: Using Multiple Key Caches for MyISAM Scalability
November 26, 2008 By 8 Comments
I have written before – MyISAM Does Not Scale, or it does quite well – two main … – create separate key cache for all actively accessed tables (assuming there are only few of them), allocating key_cache proportional to their size and load, but no more than the index size (assuming table sizes are relatively static) To…
Post: To pack or not to pack - MyISAM Key compression
May 13, 2006 By 3 Comments
… it to “key” the size reduces if PACK_KEYS=1. Might be it is some kind of special hack 
The fact MyISAM will by…) NOT NULL default ”, KEY `c` (`c`), KEY `id` (`id`) ) ENGINE=MyISAM Index size: PACK_KEYS=DEFAULT – 1550K PACK_KEYS=1 – 1453K PACK_KEYS=0 – 8176K As we… is disk bound there are more reasons to have keys packed so cache hit is better. Especially if you can get hot…
Post: MyISAM Scalability and Innodb, Falcon Benchmarks
October 12, 2007 By 10 Comments
… second confirmation that key_cache is a problem is benchmark run with disabled key_cache (=0). Results for MyISAM with key_buffer_size=0 Threads queries/sec… is comparison of MyISAM Innodb and Falcon results in the graphical form: I’ve created bug, for MyISAM key cache contention issue and lets…
Post: Crashes while using MyISAM with multiple key caches
July 18, 2009 By Leave a Comment
… multiple key caches but to online key cache resize. It is just this code most actively used in case you’re using multiple key caches. It is very rare one would resize single key cache in production and it only triggers… if you’re using multiple key caches there are often some scripts in place which adjust their size or change mappings of the…
Post: Beware: key_buffer_size larger than 4G does not work
February 14, 2007 By 17 Comments
… running MyISAM, so they set key_buffer_size to 16G… and every few days MySQL crashes. Why ? Because key_buffer_size over 4GB in size is… just fine until you have less than 4GB worth of key cache used and then it would crash. If you do not… not only fix was not made available but even maximum key_buffer_size was not restricted to safe limit. Former would be…
Post: InnoDB vs MyISAM vs Falcon benchmarks - part 1
January 8, 2007 By 117 Comments
…falcon_page_cache_size=1500M –max-connections=1500 –table-cache=512 –net_read_timeout=30 –net_write_timeout=30 –backlog=128 MyISAM / InnoDB: libexec/mysqld –no-defaults –user=root –key-buffer-size=1500M –innodb-buffer-pool-size=1500M –innodb-log-file-size=100M …
Post: Using MyISAM in production
June 17, 2006 By 35 Comments
… sure you have decent myisam_sort_buffer_size and large myisam_max_sort_file_size otherwise recovery may be done by key_cache rather than sort which can take even longer. Be careful with myisam… watch out. Lack of row cache. MyISAM tables only have indexes cached in key_buffer while data is cached in OS cache. It is performance issue…
Post: MySQL Crash Recovery
July 30, 2006 By 26 Comments
… problems. As I already wrote innodb_log_file_size and innodb_buffer_pool_size affect recovery time significantly as well as your… caches. This may reduce performance dramatically. So if you’re bringing server back after crash you might want to populate caches. For MyISAM key_cache this can be done by using LOAD INDEX INTO CACHE statement, for other storage engines…
Post: Should you move from MyISAM to Innodb ?
January 12, 2009 By 53 Comments
… primary key, caching data, higher concurrency, background flushes while on the drawbacks side we see significantly large table size (especially if data size is… for you when you’re running MyISAM but instantly break upon upgrading to Innodb. Features The MyISAM features which forbid moving to…
