…what if my database is really large, say in the multi-terabyte range? I might not be able to get enough SSD storage in…see http://www.ssdperformanceblog.com/2013/04/testing-the-micron-p320h/ – the card referenced there is…encountered is Facebook FlashCache. I’d never even heard of the STEC caching …
Post: SHOW OPEN TABLES - what is in your table cache
December 14, 2008 By 3 Comments
… rarely see this field to contain anything else than 0. Besides just figuring out what tables are in the table_cache this command is rather helpful to understand if there is activity on the given…. Another thing which would be handly is LRU position for the given table (so you can see what tables are candidates for replacement…
Post: Implications of Metadata Locking Changes in MySQL 5.5
February 1, 2013 By 9 Comments
… the Query Cache, let’s see what happens in that case. Metadata Locking and Query Cache How does metadata locking behave with query_cache? That is an important question. If Query Cache is…
Post: Should we give a MySQL Query Cache a second chance ?
April 10, 2011 By 64 Comments
… property is different from completely transparent cache and you’ll see why below. So what I think could be done with MySQL Query Cache so… quire sure if it is worth doing or if delayed invalidation is enough. Improve Manageability What is in the MySQL Query Cache ? How many hits did we get for this query item ? Right now none of such information is…
Post: What MySQL buffer cache hit rate should you target
June 29, 2006 By 5 Comments
… hit ratio 99% for what would be 0% in many peoples mind. But what is even more important is hit ratio is not directly relevant for performance. Take the following example – you have some script doing small (in… SAN cache hit rate – something you would not see otherwise. The bad luck is – MySQL currently does not provide this information (it exists in…
Post: Using MyISAM in production
June 17, 2006 By 36 Comments
…is cached in OS cache. It is performance issue as system call is needed to get data from Operation System even when it is in cache but it is…wrong result sets or crashes. Here is my list what I think MyISAM tables are… updated and as you see this is where our problems reside. Cache/Session tables (you…
Post: MySQL opening .frm even when table is in table definition cache
November 21, 2011 By 8 Comments
…is that MySQL won’t revert to opening the FRM files to read the table definition, but we can see…API is called. But back to what the above strace shows. In MySQL 5.5 you can find in sql…it already has cached (often at least twice – in InnoDB itself and in the table_definition_cache). Further reading: …
Post: How well does your table fits in innodb buffer pool ?
December 9, 2010 By 12 Comments
… because the tables and indexes they are accessing are not in cache, for example being washed away by other queries. MySQL Server… stored in buffer pool rather than using some form of temporary measures. I often check these stats during warmup to see what is really getting warmed up first as well as how buffer pool is affected by batch jobs…
Post: Side load may massively impact your MySQL Performance
November 13, 2011 By 7 Comments
… hence such drop in performance. The performance of mysqldump is impacted too because we now have 2 threads competing for what is single hard… inline with what you would expect. Lets see what is going on with buffer pool contents: INDEX_NAME DATA_SIZE_MB test.md_cache_test_small.PRIMARY 216.35031509 test.md_cache…
Post: The tool I've been waiting for years
March 18, 2008 By 10 Comments
… years to see. It is fincore – little perl script which allows you to see what pages of file are cached in OS memory. This is really cool. When it comes to MySQL it is very useful… of cache. It is about 0:50 by server clock this is why we still can see some pages remaining. Today log file is 50% in cache…
