Ceph Quick Reference

In this post you can found a lot of helpful commands that you can use with Ceph.

RBD

sudo rbd map disk_name --pool pool_name

Map the image to a block device.

sudo rbd unmap /dev/rbd/pool_name/disk_name

Unmap the image to a block device.

How to get the size of databases in MySQL

Sometimes a DB in MySQL grows without alerting the sysadmin and in this case it is helpful to have a query to identify the real dimension.

A query to get the size and free space of MySQL DB is:

SELECT table_schema "Data Base Name", 
sum( data_length + index_length ) / 1024 / 
1024 "Data Base Size in MB", 
sum( data_free )/ 1024 / 1024 "Free Space in MB" 
FROM information_schema.TABLES 
GROUP BY table_schema ;