I’m often asked how one can evaluate IO subsystem (Hard drive RAID or SAN) performance for MySQL needs so I’ve decided to write some simple steps you can take to get a good feeling about it, it is not perfect but usually can tell you quite a lot of what you should expect from the […]
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This week I already had two serious performance regression cases when upgrading from MySQL 4.0 and 4.1 to MySQL 5.0. By serious I mean several times performance difference not just 5-10% you often see for simple queries due to generally fatter code. The problem in both cases was MySQL 5.0 broken group commit bug. First […]
During the recent months I’ve seen few cases of customers upgrading to MySQL 5.0 and having serious performance slow downs, up to 10 times in certain cases. What was the most surprising for them is the problem was hardware and even OS specific – it could show up with one OS version but not in […]
When we are hired for a MySQL performance audit, we are expected to review the MySQL configuration and to suggest improvements. Many people are surprised because in most cases, we only suggest to change a few settings even though hundreds of options are available. The goal of this post is to give you a list […]
Following my previous benchmark of Samsung 830, today I want to show results for STEC MACH16 SATA card, 200GB size, this card is based on SLC, and regarding STEC website, it is an enterprise grade storage.
As you may know, Kristian Nielsen made a fix for the Group Commit Problem which we many times wrote about. The fix came into MariaDB 5.3 and Mark Callaghan tested it recently . We ported this patch to Percona Server (it is not in the main branch yet), and here are the results of my […]
One question which comes up very often is when one should use SAN with MySQL, which is especially popular among people got used to Oracle or other Enterprise database systems which are quite commonly deployed on SAN. My question in such case is always what exactly are you trying to get by using SAN ?
One of very interesting techniques Innodb uses is technique called “doublewrite” It means Innodb will write data twice when it performs table space writes – writes to log files are done only once. So why doublewrite is needed ? It is needed to archive data safety in case of partial page writes. Innodb does not […]