Category Archives: MySQL-Articles

MySQL related blog posts

04 Dec

Fixing inconsistency on MySQL Slave of Galera Cluster

Checksum is a standard practice among DBAs to verify the data consistency across replicated nodes. In this post we’re going to review the syncing options for an inconsistent MySQL slave of Galera cluster node.

Here we’re assuming a setup of regular replication to a MySQL instance from one of the Galera cluster nodes.
PXC-slave-checksum Read More

04 Nov

Setting-up second mysql instance & replication on Linux in 10 steps

We often see requirement for having multiple MySQL instances on same machine for restore, testing or backup purposes.
This post will help you configure second MySQL instance on same machine and also setup replication between them.

This is a quick setup guide of 10-steps to install and configure MySQL instance on 3307 port, and make it slave from MySQL running on port 3306. Read More

19 Oct

pt-table-checksum & Waiting to check replicas for differences: 0% 00:00 remain

I recently came across an issue where the task was to checksum databases using Percona’s pt-table-checksum. The command continued well for all the databases but when it came to specific DB, it kept on showing following error:

Waiting to check replicas for differences: 0% 00:00 remain

As this did not change for hours (was in screen session), I cross-checked that nothing blocks the process and other options!

Read More

20 Jul

MySQL 1018 (HY000): Can’t read dir errno: 13 – Permission denied

In this post we will see the resolution of MySQL “permission denied” error due to movement of database to a different partition on CentOS.

ERROR 1018 (HY000): Can’t read dir of ‘./sakila/’ (errno: 13 – Permission denied)

Recently, a friend was stuck on following issue and he was not able to access the tables under ‘sakila’ database. Though he was able to read all other databases!

ERROR 1018 (HY000): Can't read dir of './sakila/' (errno: 13 - Permission denied)

This is what happens when he try accessing the tables from sakila database:

mysql>use sakila;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> show tables;
ERROR 1018 (HY000): Can't read dir of './sakila/' (errno: 13 - Permission denied)

Read More

01 Jul

Monitoring MySQL Database Backups

It’s important to monitor the (database) backups after you set-it-up. In this post we will answer a few how to monitor MySQL Database backups solutions – monitoring methods.

We should see suggestions for:

  • Monitoring Holland MySQL Backup
  • Monitoring mysqldump backups
  • Monitoring Xtrabackup using log
  • Monitoring Backups using Nagios

Usually we can have our backup script capable of detecting the status of the backup and send an success / failure email accordingly. Alternatively the backup script can write the status to backup logs and the monitoring system should be capable of reading logs, determine the backup failure and alert.

Read More

-- Kedar Vaijanapurkar --