For me ...
Link to Munion produces:
This server could not verify that you are authorized to access the document requested. Either you supplied the wrong credentials (e.g., bad password), or your browser doesn't understand how to supply the credentials required.
Besides that ... IMHO ... of all the pieces that affect performance of a Moodle, database server config ... as well as how moodle code interacts with DB server *IS* the most important.
So have you tried installing and running MySQLTuner? And in your case, might have to run it from web server as well as DB server.
Ok, spike was present but what caused the spike? Was it mysqld?
Destination of a CLI backup was missing from command you issued ... which means moodle will use moodledata/temp/backup/ as a build area. Where is moodledata? On the same server as the web service?
One of the checks MySQLTuner makes is overall memory ... memory for DB server ... also memory for other processes server needs to function.
Here's a clip from a Moodle server that has 16Gig under VMWare virtual for a K12 entity with over 9000 users ... typically used in a blended fashion.
[--] Physical Memory : 15.6G
[--] Max MySQL memory : 4.4G
[--] Other process memory: 1.5G
[OK] Maximum reached memory usage: 3.3G (20.96% of installed RAM)
[OK] Maximum possible memory usage: 4.4G (28.44% of installed RAM)
[OK] Overall possible memory usage with other process is compatible with memory available
[OK] Slow queries: 0% (0/52M)
and of InnoDB:
[OK] InnoDB buffer pool / data size: 3.0G/2.2G
buffer pool must be larger than actual data size or DB server will suffer performance.
From same server ... top set to show what's using SWAP:
Mem: 16333820k total, 15987068k used, 346752k free, 1079616k buffers
Swap: 8208380k total, 102808k used, 8105572k free, 10316708k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ SWAP COMMAND
7706 mysql 20 0 5157m 3.5g 5168 S 0.3 22.4 201:05.56 60m mysqld
Yep, it's using SWAP ... which isn't good, but considering it's an all in one box not much wiggle room exist for tweaks. Backups cannot be run during prime time usage ... and some courses require CLI backup on weekends when site isn't used as much as 'prime time' during week.