20 GIG does seem a bit large. I'm running 16 cameras with mocord on a 1 TB drive and the database totals less than 700 MEG. Somewhere over 31,000 events are on the drive. I have converted MySQL to use INNODB_FILE_PER_TABLE which may help you.
Procedure follows:
Enable and convert MySQL to innodb_file_per_table for Zoneminder
Note: You may wish to convert MyISAM tables to InnoDB tables before you proceed. Upgrading Zoneminder to 1.26 or newer should do this for you.
innodb_file_per_table is by default ON Mysql 5.6.6 and onwards. There is plenty of stuff on Google about pros & cons of innodb_file_per_table.
This post details how to enable innodb_file_per_table on an existing database. Because innodb_file_per_table affects new tables only, created after innodb_file_per_table is enabled, we need to recreate old databases to force innodb_file_per_table on old tables and reclaim some disk space.
Become root
sudo su
Backup First
Create a dir to take backups:
cd ~
Note: I found it helpful to create a file which contained the MySQL user and password. Otherwise you will have to enter the user and password for every operation.
nano .my.cnf
Enter this content
[client]
user=root
password=mysqlpass
(Naturally, use your MySQL password in the above script...)
Ctrl+o Enter to save
CTRL+x to exit
Make backup directory
mkdir backup
cd backup
Copy MySQL data files (raw)
(If all goes well, we will not need this)
Stop Zoneminder
service zoneminder stop
If you have other services that use MySQL you will want to stop them and possibly Apache.
service mysql stop && cp -ra /var/lib/mysql mysqldata && service mysql start
Take mysqldump
As soon as above line completes, take a mysqldump of all databases
mysqldump --routines --events --flush-privileges --all-databases > all-db.sql
Drop Databases
Create a sql file to drop all databases EXCEPT mysql database
mysql -e "SELECT DISTINCT CONCAT ('DROP DATABASE ',TABLE_SCHEMA,' ;') FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA <> 'mysql' AND TABLE_SCHEMA <> 'information_schema';" | tail -n+2 > drop.sql
Verify if drop.sql has correct database names and then execute drop.sql queries.
mysql < drop.sql
Verify all InnoDB tables gone
SELECT table_name, table_schema, engine FROM information_schema.tables WHERE engine = 'InnoDB';
Remove InnoDB files
Stop mysql server first
service mysql stop
Then
rm /var/lib/mysql/ibdata1 && rm /var/lib/mysql/ib_logfile0 && rm /var/lib/mysql/ib_logfile1
At this point most likely you will have only /var/lib/mysql/mysql directory only.
Enable innodb_file_per_table
Open my.cnf file
nano /etc/mysql/my.cnf
Add following line after [mysqld]
innodb_file_per_table
Ctrl+o Enter to save
CTRL+x to exit
Time to import from mysqldump
Start mysql server now
service mysql start
Run mysql import
mysql < all-db.sql
Force mysql_upgrade (to generate performance_schema)
mysql_upgrade --force
That’s All!
Restart Zoneminder (and any other services you have stopped)
service zoneminder start
Check for proper operation and that all your events are present.
When you are satisfied that all is worling well remove the backup directory and password filr=e
cd ~
rm backup
rm .my.cnf
You are finished!
This procedure has been adopted from
https://rtcamp.com/tutorials/mysql/enab ... -per-table. Thanks to Rahul Bansal!