WordPress going offline for some minutes in some database-intensive activities

What do you mean by MySQL goes offline? What error do you get on the page? Is it a “freeze” of pages or an actual DB error connection?

If the DB is actually shutdown, you should be able to see a shutdown/startup in the error log. Otherwise I’d suspect your DB engine is MyISAM, which does table level locks (vs row-level locks) on the whole table and makes editing posts simultaneously not possible.

Run these commands to get a feel of things:

mysql -u root -e "show table status" unixy_whmcs1|grep -i myisam

If you get many MyISAM tables, it’s probably time to switch to InnoDB.

Cheers

Yes I’d definitely switch to InnoDB. This issue would go away. Here’s a quick one liner:

mysql -u root -e "show tables" <my_db> | while read tbl; do echo mysql -u root -e "alter table ${tbl} engine=InnoDB" <my_db>; done