Storage Spaces Tiers optimization - how to disable totally ?

Hello,

Is Storage Spaces tiering optimization happens automatically then Storage Spaces thinks it has to be done ?

In my server i have set "Storage Tiers Optimization" task in task scheduled run every Saturday 13:00 and if i look at tasks jobs history i see that it does so.

PS C:\Windows\system32> Get-ScheduledTask -TaskName *Tier*  | Get-ScheduledTaskInfo

LastRunTime        : 2014-06-28 13:00:00
LastTaskResult     : 0
NextRunTime        : 2014-07-05 13:00:00
NumberOfMissedRuns : 0
TaskName           : Storage Tiers Optimization
TaskPath           : \Microsoft\Windows\Storage Tiers Management\
PSComputerName     :

But if i look at event viewer - Windows\Storage-Tiering\Admin log i see that beside Saturdays optimization jobs happens several times a week.

Why it happens ? How to stop it from happening ? It looks that if i make a lot of writes to it at night it starts to optimize.

Need to stop it because for unknown reason if DPM starts to backup VM from this server while tiers optimization running - VHD's for VMs gets read only.