Hello all, This post is in preparation of an upgrade of Mysql 3.23.58 to 4.x OS: Fedora Core 2 Plesk: 7.5.4 QUESTIONS 1. 4.1 or 4.0.x ? 2. Know Issues 3. Applications incompatibility ( like vault apps ) 4. update source? ( mysql.org rpms, ART yum repository, others? ) WHAT I ALREADY KNOW - If upgrading to 4.0.x, will need to update grant tables - If upgrading to 4.1, will need to set old_passwords=1 in my.cnf After all my research, reading mysql.org recomendations, reading forums here, contacting my colocation provider's tech support this is what I have I would now like to move forward and perform my upgrade, since this is a production server I wish to be really careful and document all the possible issues and steps to be taken before taking action and transform that 30 minutes downtime window to 72 hours! If you have anything to suggest, any experience to share, please go ahead!