It seems pretty common to find customers install DRBD for the wrong reasons. There are many pros/cons to compare DRBD to replication, but I’ve managed to cut down my spiel I give to customers to these two points: DRBD’s aim (assuming replication mode C) is to provide 100% consistency, and then as much uptime as [...]
What does Using filesort mean in MySQL?
March 5, 2009 By 27 Comments
If you were interviewing to work at Percona, and I asked you “what does Using filesort mean in EXPLAIN,” what would you say? I have asked this question in a bunch of interviews so far, with smart people, and not one person has gotten it right. So I consider it to be a bad interview [...]
Beware of MySQL Data Truncation
February 7, 2009 By 4 Comments
Here is nice gotcha which I’ve seen many times and which can cause just a minefield for many reasons. Lets say you had a system storing articles and you use article_id as unsigned int. As the time goes and you see you may get over 4 billions of articles you change the type for article_id [...]
MySQL QA Team Benchmarks for MySQL 5.1.30
December 13, 2008 By 12 Comments
As you might have seen MySQL QA Team has published their benchmarks for MySQL 5.0.72 and 5.1.30. It is interesting to compare with results I posted previously
How Percona does a MySQL Performance Audit
November 24, 2008 By 17 Comments
Our customers or prospective customers often ask us how we do a performance audit (it’s our most popular service). I thought I should write a blog post that will both answer their question, so I can just reply “read all about it at this URL” and share our methodology with readers a little bit. This [...]
How adding another table to JOIN can improve performance ?
August 1, 2008 By 12 Comments
JOINs are expensive and it most typical the fewer tables (for the same database) you join the better performance you will get. As for any rules there are however exceptions The one I’m speaking about comes from the issue with MySQL optimizer stopping using further index key parts as soon as there is a range [...]
Neat tricks for the MySQL command-line pager
June 23, 2008 By 12 Comments
How many of you use the mysql command-line client? And did you know about the pager command you can give it? It’s pretty useful. It tells mysql to pipe the output of your commands through the specified program before displaying it to you. Here’s the most basic thing I can think of to do with [...]
Confusing MySQL Replication Error Message
June 4, 2008 By 11 Comments
I already wrote about some MySQL Error Messages which are confusing, here is one more:
1 2 3 4 5 6 7 8 9 10 | 080603 20:53:10 [Note] Slave: connected to master 'repl@host.com:3306',replication resumed in log 'master-bin.003676' at position 444286437 080603 20:53:10 [Note] Slave: received end packet from server, apparent master shutdown: 080603 20:53:10 [Note] Slave I/O thread: Failed reading log event, reconnecting to retry, log 'master-bin.003676' position 444292333 080603 20:53:10 [Note] Slave: connected to master 'repl@host.com:3306',replication resumed in log 'master-bin.003676' at position 444292333 080603 20:53:10 [Note] Slave: received end packet from server, apparent master shutdown: 080603 20:53:10 [Note] Slave I/O thread: Failed reading log event, reconnecting to retry, log 'master-bin.003676' position 444294573 080603 20:53:10 [Note] Slave: connected to master 'repl@host.com:3306',replication resumed in log 'master-bin.003676' at position 444294573 080603 20:53:10 [Note] Slave: received end packet from server, apparent master shutdown: 080603 20:53:10 [Note] Slave I/O thread: Failed reading log event, reconnecting to retry, log 'master-bin.003676' position 444298239 080603 20:53:10 [Note] Slave: connected to master 'repl@host.com:3306',replication resumed in log 'master-bin.003676' at position 444298239 |
After setting up new slave Server I’m getting error log file flooded with messages like this and there is no hint in the message what would explain what is wrong. In fact the issue in this case is (because [...]
Should you name indexes while doing ALTER TABLE ?
May 28, 2008 By 10 Comments
MySQL Server does not require you to specify name of the index if you’re running ALTER TABLE statement – it is optional. Though what might be good practical reasons to specify the key name or omit ? Things what you should be looking at is how MySQL names indexes automatically as well as what maintaining [...]
Site was down today, support and web hosting.
August 31, 2007 By 27 Comments
During last one and a half year we had pretty good track record with MySQL Performance Blog – there were times when site was slow (especially when backup was running) but I do not remember significant downtime, until today we went down for few hours. All this time the site was running on dedicated server [...]
