Top critical review
Great drives but the EFAX line of WD Reds are Shingled Magnetic Drive (SMR) HDDs
Reviewed in Canada on July 16, 2020
WD Reds are for continuous, always on NAS use. However, any Red Drive that has EFAX in its part number is a Shingled Magnetic Recording SMR) drive where tracks partially overlap each other (hence the term shingled). They work great until they don't. If an SMR drive fails in your NAS and you replace it, rebuild time is reported to be in the order of weeks, not hours. Best to find a detailed technical article as to why this is but in a nutshell, from now on, I am going to avoid all SMR technology drives in general and all WD Red drives with EFAX in their part numbers.
BTW, WD makes Red drives that use conventional magnetic recording (CMR). Any WD Red drive with EFRX in its part number is a CMR drive and rebuild time will be on the order of hours. And the CMR drives don't really cost any more.
FInally, WD is being sued (class action pending) for selling SMR drives in always-on NAS use because rebuild times of days to weeks is inconsistent with the needs of the NAS market.
WD is still a great maker, just be sure to avoid the EFAX drives in NAS applications.