April 20, 2014

Using XtraBackup on NFS for MySQL backups

XtraBackup works great for backing MySQL up to an NFS volume, but there is a gotcha that you need to be aware of. This applies to anything you do with NFS, not just XtraBackup. The gotcha is that NFS uses client-side caching to reduce overhead of sending data across the network.

An argument for not using mysqldump

I have a 5G mysqldump which takes 30 minutes to restore from backup.  That means that when the database reaches 50G, it should take 30×10=5 hours to restore.  Right?  Wrong.

Pacemaker, please meet NDB Cluster or using Pacemaker/Heartbeat to start a NDB Cluster

Customers have always asked me to make NDB Cluster starts automatically upon startup of the servers. For the ones who know NDB Cluster, it is tricky to make it starts automatically. I know at least 2 sets of scripts to manage NDB startup, ndb-initializer and from Johan configurator www.severalnines.com. If all the nodes come up […]

How to generate per-database traffic statistics using mk-query-digest

We often encounter customers who have partitioned their applications among a number of databases within the same instance of MySQL (think application service providers who have a separate database per customer organization … or wordpress-mu type of apps). For example, take the following single MySQL instance with multiple (identical) databases:

Crashes while using MyISAM with multiple key caches

Over last couple of years I have ran into random MySQL crashes in production when multiple key caches were used. Unfortunately this never was frequent or critical enough issue so I could spend time creating repeatable test case and search of the bug in the MySQL database did not find anything. Recently we had this […]

Using netcat to copy MySQL Database

This is mainly a cheat sheet for me to remember. Nothing rocket science. It often makes sense to use netcat/nc to copy MySQL database between hosts in trusted networks. It bypasses encryption overhead of SSH and depending on configuration can be significantly faster. Also note MySQL should be down when you copy data unless you’re […]

What does Using filesort mean in MySQL?

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 […]

Using Multiple Key Caches for MyISAM Scalability

I have written before – MyISAM Does Not Scale, or it does quite well – two main things stopping you is table locks and global mutex on the KeyCache. Table Locks are not the issue for Read Only workload and write intensive workloads can be dealt with by using with many tables but Key Cache […]

Using INFORMATION_SCHEMA instead of shell scripting

INFORMATION_SCHEMA, in particular by favorite TABLES table is not only helpful to understand tables you have on the system, but I have also found it to be very helpful as a scripting language for variety of database administration tasks. It can be more straightforward compared to using shell or Perl when the operation is database […]

Confusing MySQL Replication Error Message

I already wrote about some MySQL Error Messages which are confusing, here is one more:

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 […]