Symptom
You set the "Storage Tiers Optimization" task in Task Scheduler and run it every Saturday 1:00 AM. However, you may find that optimization jobs happens several times a week when look at event viewer - Windows\Storage-Tiering\Admin log.
Reproduce Steps:
Configure Storage Tiers in Windows Server 2012 R2, then check the Storage Tiers Optimization task in Task Scheduler\Microsoft\Windows\Storage Tiers Management. The task runs at 1:00 am every day.(Figure 1)
Figure 1
However, when you check the event viewer, under Applications and Services Logs\Microsoft\Windows\Storage-Tiering\Admin log. The optimization jobs also starts other time besides 1:00 AM. It is not scheduled. (Figure 2 & 3)
Figure 2
Figure 3
Cause
In Windows server 2012 R2, by default there are two tasks which would trigger storage tier optimization:
1. Defrag task - found under \Microsoft\windows\defrag
This task runs on weekly basis.
2. Storage tier optimization - found under \Microsoft\windows\storage tiers management
This task runs on daily basis.
Apart from the above 2 tasks, if a user runs "tier optimization task" manually, using "defrag.exe with /g flag" or "optimize-volume with -tierOptimize" cmdlet, windows would log an event in the event viewer when the optimization task completes.
More Information
Monitor Storage Tiers Performance in Windows Server 2012 R2
http://technet.microsoft.com/en-us/library/dn789160.aspx
What's New in Defrag for Windows Server 2012/2012R2
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