April 20, 2014

How FLUSH TABLES WITH READ LOCK works with Innodb Tables

Many backup tools including Percona Xtrabackup, MyLVMBackup and others use FLUSH TABLES WITH READ LOCK to temporary make MySQL read only. In many cases the period for which server has to be made read only is very short, just few seconds, yet the impact of FLUSH TABLES WITH READ LOCK can be quite large because […]

How to know if you’re updating Slave you should not ?

When replication runs out of sync first question you often ask is if someone could be writing to the slave. Of course there is read_only setting which is good to set in the slave but it is not set always and also users with SUPER privilege bypass it. Looking into binary log is obvious choice […]

Btw xtrabackup is not only backup..

It is obvious thing for me, but I just figured out it may be not common understanding. Xtrabackup is also can be used (not only can, but we actually use it this way) to clone one slave to another, or just setup new slave from the master. And it is done in almost non-blocking way […]

How SHOW SLAVE STATUS relates to CHANGE MASTER TO

As you probably know MySQL Replication (statement based) works by fetching statements from MASTERs binary log and executing them on the SLAVE. Since MySQL 4.0 this process is a bit more involved having events passing via relay logs on the Slave which also means there are two replication threads “IO Thread” and “SQL Thread” used […]

Managing Slave Lag with MySQL Replication

The question I often get is how far MySQL may fall behind and how to keep replication from lagging. The lag you will see will vary a lot from application to the application and from load to load. Plus what is the most important within same application the lag will likely have spikes – most […]

Master-Master or Master with Many Slaves

I just found post by Kevin, in which he criticizes Master-Master approach, finding Master with many slaves more optimal. There is surely room for master-N-slaves systems but I find Master-Master replication much better approach in many cases. Kevin Writes “It requires extra hardware thats sitting in standby and not being used (more money and higher […]

Getting use of Slave in MySQL Replication

MySQL Replication is asynchronous which causes problems if you would like to use MySQL Slave as it can contain stale data. It is true delay is often insignificant but in times of heavy load or in case you was running some heavy queries on the master which not take time to replicate to the slave […]

percona-millipede – Sub-second replication monitor

I recently helped a client implement a custom replication delay monitor and wanted to share the experience and discuss some of the iterations and decisions that were made. percona-millipede was developed in conjunction with Vimeo with the following high-level goal in mind: implement a millisecond level replication delay monitor and graph the results.  Please visit […]

ScaleArc: Benchmarking with sysbench

ScaleArc recently hired Percona to perform various tests on its database traffic management product. This post is the outcome of the benchmarks carried out by Uday Sawant (ScaleArc) and myself. You can also download the report directly as a PDF here. The goal of these benchmarks is to identify the potential overhead of the ScaleArc […]

Innodb redo log archiving

Percona Server 5.6.11-60.3 introduces a new “log archiving” feature. Percona XtraBackup 2.1.5 supports “apply archived logs.” What does it mean and how it can be used? Percona products propose three kinds of incremental backups. The first is full scan of data files and comparison the data with backup data to find some delta. This approach […]