Verifying RAID

I have 4 x 8TB WD Red in my DL4100, and setting up the RAID I could start use it after relative short time, but - it kept “Verifying RAID” for 24+ hours

What is really happening in this verification time?

Kinda like the difference between format quick and regular. It can create the raid quickly and just throw data at t or it can verify that all the little x and o’s work in the background.

Verify is normally a low priority so it takes time, but you can still use your system