WD black or RAID causing lag?

Back in January, I built a new system using 2 x 2TB WD Black internal HDs. It is set up as RAID 1. Almost every day, at some point, my PC seems to “Hang” or lag for anywhere from several seconds up to almost 20 seconds. It doesn’t seem to matter what I’m doing- it can be something as simple as trying to open a folder in Windows explorer. I am trying to determine what is causing the lag- the HDs or possibly the RAID. Is this normal? The WD Black Hard Drives are used for storage only- the operating system is installed on a 120 GB Samsung SSD. I have 32 GB RAM, Windows 8.1.  

I would remove the blacks and test the SSD without the blacks

I had freezes on my pc and the problem was the SSD dying… it evntualy stopped appearing in BIOS and i lost some data

Hmm…hope it’s not the SSD. It’s only 7 months old.

Mine died with about 130 days use on smart 1.50TB used… wasnt able to be detected