![Amazon.com: Western Digital 4TB WD Red NAS Internal Hard Drive HDD - 5400 RPM, SATA 6 Gb/s, SMR, 256MB Cache, 3.5" - WD40EFAX : Electronics Amazon.com: Western Digital 4TB WD Red NAS Internal Hard Drive HDD - 5400 RPM, SATA 6 Gb/s, SMR, 256MB Cache, 3.5" - WD40EFAX : Electronics](https://m.media-amazon.com/images/I/710aEelzoRL._AC_UF1000,1000_QL80_.jpg)
Amazon.com: Western Digital 4TB WD Red NAS Internal Hard Drive HDD - 5400 RPM, SATA 6 Gb/s, SMR, 256MB Cache, 3.5" - WD40EFAX : Electronics
![NAS Compares - SMR, CMR and PMR NAS Hard Drives- A Buyers Guide 2021 | SynoForum.com - The Unofficial Synology Forum NAS Compares - SMR, CMR and PMR NAS Hard Drives- A Buyers Guide 2021 | SynoForum.com - The Unofficial Synology Forum](https://www.synoforum.com/proxy.php?image=https%3A%2F%2Fnascompares.com%2Fwp-content%2Fuploads%2F2021%2F04%2FCMR-PMR-HARD-DRIVE-PLATTER.png&hash=851539a9c8e5c4f0937dfbbda2862b8c)
NAS Compares - SMR, CMR and PMR NAS Hard Drives- A Buyers Guide 2021 | SynoForum.com - The Unofficial Synology Forum
![Seagate to Expand Usage of SMR - The Evolution of HDDs in the Near Future: Speaking with Seagate CTO, Mark Re Seagate to Expand Usage of SMR - The Evolution of HDDs in the Near Future: Speaking with Seagate CTO, Mark Re](https://images.anandtech.com/doci/10218/seagate_hdd_areal_emerging_smr.png)