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System size and Performance Optimization

 | February 27, 2007 |  Posted In: Insight for Developers

Performance optimization is never ending story, you can virtually always find something else to optimize but while on generic system, not tuned by expert you often can get significant performance increase in the matter of hours further performance improvements become more and more time consuming and expensive and gains smaller. This observation does not only […]

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Pitfalls of converting to InnoDB

 | February 25, 2007 |  Posted In: Insight for DBAs

We often recommend to our clients to convert their current database from MyISAM tables to InnoDB. The transfer by itself in most cases is almost plain, however the application can be broken by new unexpected errors 1205 (ER_LOCK_WAIT_TIMEOUT) Lock wait timeout expired. Transaction was rolled back. 1213 (ER_LOCK_DEADLOCK) Transaction deadlock. You should rerun the transaction.

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MySQL Error control changes

 | February 19, 2007 |  Posted In: Insight for Developers

In MySQL 5.0 mainly error control was improved, such as strict mode was added to change famous MySQL behavior of cutting too large strings, too big numbers and allowing you to use dates such as February 31st. In one case however reverse change was done – in regards to storage engine initialization. Previously if you […]

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Beware: key_buffer_size larger than 4G does not work

 | February 14, 2007 |  Posted In: Insight for DBAs

I was working with customer today which has MySQL on a system with some 64GB or RAM 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 not really supported (checked with latest and greatest MySQL Enterprise 5.0.34). It works just fine […]

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Getting use of Slave in MySQL Replication

 | February 14, 2007 |  Posted In: Insight for Developers

MySQL Replication is asynchronous which causes problems if you would like to use MySQL Slave as it can contain stale data. It is true delay is often insignificant but in times of heavy load or in case you was running some heavy queries on the master which not take time to replicate to the slave […]

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Content delivery system design mistakes

 | February 11, 2007 |  Posted In: Insight for Developers

This week I helped dealing with performance problems (part MySQL related and part related to LAMP in general) of system which does quite a bit of content delivery, serving file downloads and images – something a lot of web sites need to do these days. There were quite a bit of mistakes in design for […]

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Debugging sleeping connections with MySQL

 | February 8, 2007 |  Posted In: Insight for DBAs

Have you ever seen connection in the SHOW PROCESSLIST output which is in “Sleep” state for a long time and you have no idea why this would happen ? I see if frequently with web applications and it is often indication of trouble. Not only it means you may run out of MySQL connections quicker […]

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Why do you need many apache children ?

 | February 5, 2007 |  Posted In: Insight for Developers

I already wrote kind of about same topic a while ago and now interesting real life case makes me to write again 🙂 Most Web applications we’re working with have single tier web architecture, meaning there is just single set of apache servers server requests and nothing else – no dedicated server for static content, […]

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