Space not reclaimed after dropping MyISAM table
If you dropped a 4GB MyISAM table and still have 100% usage of the disk, then something else is clogging up the disk. This is especially true if /var/lib/mysql is on the same mount and /root.

Here is what you can do to start investigating: Go to the OS and do this:

cd /var/lib/mysql
df -h .


If the root partition is 100% despite dropping 4GB,


your datadir is not var/lib/mysql
another table consumed up the space quickly
something else clogged the root partition


Who are the usual suspects ?


Binary Logs : You cannot run PURGE BINARY LOGS with a 100% full disk. You will have to locate the folder with the binary logs, delete the oldest ones, and mysqld will get moving.
Error Log : Just a text file. Suppose your error log is /var/log/mysqld.log. You run echo -n &gt; /var/log/mysqld.log and the space from that file is reclaimed. I don't use rm since mysqld has an open file handle to the error log.
Slow Log : Locate the Slow Log and do the same thing as you did with the Error Log
Temp Tables : These are usually created in /tmp. If you see .MYD file in /tmp with old timestamps, you can manually delete them.


Whatever it is, find the offending files and delete/truncate them because mysqld will not crash on Error 28 (Out of Disk Space). The mysqld will pause and wait patiently for diskspace to be available (See my post &quot;Site Offline&quot; MySQL server failing to start and stop).