Why are the hard disks on a Windows Home Server always active?

Why are the hard disks on a Windows Home Server always active?

They are always running and making a noise as if they are constantly being read from and written to.

The culprit it's demigrator (drive extender migrator) It's a system service that every now and then compares the content of ALL the drives in the storage pool and syncs the files between the disks.

It can cause a big slowdown sometimes (50% of cpu time in my server). That's why Microsoft dumped the drive extender feature in VHSv2/Vail/Fail

I schedule to run it when I don't use the server

Download processexplorer and see if there's a process that is active. It's part of the free sysinternals suite. There should also be process monitor and/or file monitor that should tell you about process and disk activity. It's possible that something is using the server's disks.

You should also check the logs to see if something is showing up there.

I noticed this in mine as well. There's a process out there that is constantly (like every 30 minutes it seems) doing load balancing to spread the files in your shares over multiple disks. File duplication increases the work this process needs to do as it has to make sure every file is on at least 2 separate disks.

Probably there is some process running that's thrashing the disks - I concur with the previous answer of Process Explorer.

One other possibility, though, since you don't specify that you hear heads clicking, just noise from the disks - if you have power management settings set to max performance oftentimes the disks will never spin down (this prevents any delay on the next disk access). This should be configurable in the advanced power options.