We have had performance issues for a few weeks at night, all our Hyper-V Servers where performing like CRAP every night around 3 AM and for about 45 minutes.
After a long night of investigation with my colleague, we found out that Windows 2012 is running a maintenance job around 03:00 each day.
When we stopped it all began to run as normal. This caused overloading of the SAN SP and gave high disk queue on all servers attached to the SAN.
But, after we disabled the Scheduled Task “Regular Maintenance“, it got enabled Again after some hours.
To avoy this disable “Maintenance Configurator“, but this can´t be done from GUI
To disable Maintenance Configurator run this command on a server with PsExec Link :
psexec \\SERVERNAME -s schtasks /change /tn "\Microsoft\Windows\TaskScheduler\Maintenance Configurator" /DISABLE