Comment 10 for bug 1592749

Lars,

I am sorry. First, I had installed MariaDB and so the failures were for MariaDB and not MySQL.
MariaDB is more than 10 times slower than PostgreSQL, and it shows very clearly in iostat and perf top output. iostat shows much higher iowait numbers than PostgreSQL, it appears that most of the difference in performance is just MariaDB (and thus probably MySQL) sitting waiting for I/Os.

Unfortunately after installing MariaDB, it is not possible to remove (purge) MariaDB and then re-install MySQL. The installation of the server always fails, and I get lots of problems such as Can't connect to local MySQL server through socket ... as well of errors saying that the unix_socket plugin is not installed. One of the things I could not do was to compare the default my.cnf files on 14.04 and 16.04 to see if anything that could change the "out-of-the-box" performance changed.

At this point, I have to give up, because I have too many urgent projects pressing on my. I am convinced that there is a serious performance problem on both MySQL and MariaDB compared to PostgreSQL when working with Bacula and both being untuned.

I also think there is a "bug" in apt-get purge of MariaDB server that leaves some traces of MariaDB lying around so that a subsequent install of MySQL fails -- that probably should be the subject of another bug report. I see there is lots of advice on the web for fixing this problem, but I keep running into problems such as no mysql_safe, ... It is so bad that even apt-get purge mysql-server fails in horrible ways.
Running as root:

======================
apt-get purge mysql-server mysql-client
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package 'mysql-client' is not installed, so not removed
Package 'mysql-server' is not installed, so not removed
0 upgraded, 0 newly installed, 0 to remove and 43 not upgraded.
1 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Setting up mysql-server-5.7 (5.7.12-0ubuntu1.1) ...
mysql_upgrade: Got error: 1524: Plugin 'unix_socket' is not loaded while connecting to the MySQL server
Upgrade process encountered error and will not continue.
mysql_upgrade failed with exit status 11
dpkg: error processing package mysql-server-5.7 (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 mysql-server-5.7
E: Sub-process /usr/bin/dpkg returned an error code (1)

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I would really like to find out what is hurting the performance, but it will have to wait to a later time.