… they cancel out. The key cache hit ratio is simply one minus the miss ratio. The key_buffer hit ratio The metrics we’re interested in…:100″ or “your key cache hit ratio should be very high, ideally above 99.9%” or “if your key cache hit ratio is low, your key… the short version is: ratio-based tuning is just as wrong for InnoDB as it is for MyISAM. Ratio-based tuning is invalid…
Post: What MySQL buffer cache hit rate should you target
June 29, 2006 By 5 Comments
… cache hit rate is good for optimal MySQL Performance” is typical question I’m asked. It could by MyISAM key_buffer or Innodb innodb… to be understand is – cache hit ratio can be computed differently for different engines. For example for Innodb page hits are counted for all subsequent…
Post: Why don't our new Nagios plugins use caching?
February 19, 2012 By 1 Comment
…; I didn’t cache the data retrieved from MySQL, I cached the resulting metrics. This avoids having to do InnoDB parsing repeatedly, too… shortcoming. I did not like writing my own cache management code. Handling cached data correctly is one of the two hard things… monitoring program’s silly “alert on 99 different kinds of cache hit ratio thresholds” approach, you’ll soon have sysadmins with /dev/null…
Post: SHOW INNODB STATUS walk through
July 17, 2006 By 40 Comments
…. Ratio of number of merges to number of inserts is pretty much insert buffer efficiency. Adaptive hash index is hash index Innodb… or less expensive. If innodb_flush_logs_at_trx_commit=2 log writes are done to OS cache, and being sequential writes… pool hit ratio which measures buffer pool efficiency. 1000/1000 corresponds to 100% hit rate. It is hard to tell what buffer pool hit…
Comment: Choosing innodb_buffer_pool_size
January 13, 2009 By 38 Comments
…, if your innodb_buffer_pool is FULL (indicated by “Free buffers”) and you still don’t have everything cached (Buffer pool hit rate… than the response time you get while building up the cache. Example, say you have 100 processes reading off the database… to 20ms while cache is building up (free buffer decrease, cache hit ratio increase). But now, your cache is full and your cache hit ratio is at 95…
Post: What to tune in MySQL Server after installation
September 29, 2006 By 116 Comments
… set but it will crawl with default innodb_buffer_pool_size. Also Innodb buffer pool caches both data and index pages so you do not need to leave space for OS cache so values… and see if it is well used. For certain workloads cache hit ratio is lower than would justify having it enabled. Note: as…
Post: Predicting Performance improvements from memory increase
August 7, 2008 By 6 Comments
… we predict the benefit from increasing the memory and so cache sizes ? I typically start by looking at the type of… a lot of CPU idle and not because of internal Innodb limits but because your application logical serialization problems. So what… estimations and take IO subsystem into account – even with same cache hit ratio more data and more load means there are higher demands…
Comment: 128GB or RAM finally got cheap
August 4, 2008 By 14 Comments
… the cases I’ve seen it was actually used for Innodb buffer pool. 100GB Buffer pool this is sweet (though counting… sec). But anyway we should not mix concurrency issues with cache hit ratio. If you’re consolidating 4 32GB boxes to 1 128GB… still much faster than disk. And well… we should fix Innodb so there is no single mutex used 
Comment: What to tune in MySQL Server after installation
October 23, 2006 By 116 Comments
… iteratively tune this parameters. For instance, INNODB_BUFFER_POOL_SIZE… how can I evaluate hit ratios to determine if this is undersized? Sure… the query cache and key cache? I’ve noticed in the Administrator GUI tool you can see hit ratios for query cache and key cache in…
Post: Living with backups
November 6, 2008 By 28 Comments
… significantly degraded performance. Anything else? All modern systems usually use caching of whatever is being read from a storage. It allows… random “garbage” for no good reason. Since the hit ratio becomes worse as the cache is being filled with random information additional I… it right. Even though it’s always the case for InnoDB tablespaces, other MySQL data files do not comply with this…
