If you read Percona’s whitepaper on Goal-Driven Performance Optimization, you will notice that we define performance using the combination of three separate terms. You really want to read the paper, but let me summarize it here: Response Time – This is the time required to complete a desired task. Throughput – Throughput is measured in […]
I recently had a run-in with a very popular PHP ecommerce package which makes me want to voice a recurring mistake I see in how many web applications are architected. What is that mistake? The ecommerce package I was working with depended on caching.Â Out of the box it couldn’t serve 10 pages/second unless I […]
So you get MySQL or other applications using too much memory on the box or OS behaving funny and using more memory for cache and pushing application to the swap. This causes swapping and causes performance problems. This much is obvious. But how bad is it ? Should you count it same as normal Disk […]
I can think of at least two major reasons why systems delay flushing changes to durable storage: 1. So they can do the work when it’s more convenient. 2. So they can do less work in total. Let’s look at how the second property can be true.
I have run into a number of cases recently that all had a similar look and feel. In most of these cases, the symptoms were very complicated, but they boiled down to just a few problems that can be prevented in very simple ways. If you are not doing any of the following three simple […]
I see a lot of people filtering replication with binlog-do-db, binlog-ignore-db, replicate-do-db, and replicate-ignore-db. Although there are uses for these, they are dangerous and in my opinion, they are overused. For many cases, there’s a safer alternative.
I had a call with Monty the other day and I told him why I think MySQL Server Quality will never be the same again. I’ve been thinking a bit more about it and here is the extended list. In particular I think MySQL Server will never be able to reach its original quality guidelines […]
Recently I was tasked with investigating slippage between master and slave in a standard replication setup. The client was using Maatkit’s mk-table-checksum to check his slave data was indeed a fair copy of that of the master.
Take a look at this:
mysql> repair table a3;
| Table | Op | Msg_type | Msg_text |
| test.a3 | repair | status | OK |
1 row in set (0.10 sec)
mysql> select * from a3 order by i;
| i |
| 2147483648 |
| 11 |
| 13 |
| 14 |
| 2147483647 |
5 rows in set (0.00 sec)
The sort order is obviously wrong while CHECK TABLE is not reporting any error
Do you have skip_name_resolve set in your /etc/my.cnf? If not, consider it. DNS works fine, until it doesn’t. Don’t let it catch you off guard. Do you really need to restrict MySQL users based on hostnames? If you don’t, you should probably disable this feature of MySQL’s authentication system. You never know when your hosting […]