miércoles, 20 de febrero de 2008

Migrating the platform to mysql 5.1

Last week I began the actualization of the server platform (CentOS versión, MySQL version, GFS version) for the dwh I manage.

Everything went quite right except the MySQL upgrade (from 5.0 to 5.1). As you may know MyISAM tables are composed by three files: a frm file that contains information of the table structure, a myd file that contains the data and a myi file that contains the index data. The MyISAM structure didn't change from 5.0 to 5.1 so I just did a copy of the files....but that was not totally true for ARCHIVE engine...

The ARCHIVE engine is a compressed data table which allow less disk usage (you should know disk usage is important for DWH :)) ...the scans are fater because rows are compressed and the server can read more rows from disk (obviously with the penalty of processor time for decompression). I use ARCHIVE for historic and less frequently queried tables...

So what was the problem? MySQL 5.1 crashes on some (not all) ARCHIVE tables....I am working around this problem.....