Update TNHardwareGuide.md

static/includes/TNHardwareGuide.md

@@ -52,11 +52,21 @@ Enterprise SATA disks address the always-on factor, vibration tolerance, and dri
 However, the price gap between desktop and enterprise SATA drives is so vast that many users push their consumer drives into 24/7 service pursuing cost savings.
 
 Drive vendors, likely tired of honoring warranties for failed desktop drives used in incorrect applications, responded to this gap in the market by producing NAS drives.
-NAS drives achieved fame from the original Western Digital (WD) Red™ drives with CMR/PMR technology (now called WD Red Plus).
+NAS drives achieved fame from the original Western Digital (WD) Red™ drives with [Conventional Magnetic Recording (CMR)](https://en.wikipedia.org/wiki/Perpendicular_recording) technology (now called WD Red Plus).
 Western Digital designed the WD Red™ Plus NAS drives (non-SMR) for systems with up to 8 hard drives, the [WD Red™ Pro](https://www.westerndigital.com/products/internal-drives/wd-red-pro-sata-hdd) for systems with up to 16 drives, and the [WD UltraStar™](https://www.westerndigital.com/products/data-center-platforms) for systems beyond 16 drives.
 
 The iXsystems Community Forum prefers WD drives for TrueNAS builds due to their exceptional quality and reliability.
 All TrueNAS Minis ship with WD Red™ Plus drives unless requested otherwise.
+
+{{< hint type=warning title="TrueNAS and SMR Drives" >}}  
+Drive manufacturers produce SATA NAS disks that use either CMR or [Shingled Magnetic Recording (SMR)](https://en.wikipedia.org/wiki/Shingled_magnetic_recording) technology.  
+SMR drives offer greater storage density compared to their CMR equivalents.
+However, due to slower write and overwrite performance (rewriting over existing data) and the potential for instability or even data loss during resilver operations, iXsystems [does not recommend]({{< relref "/hardware/notices/wdsmr.md" >}}) using SMR drives with TrueNAS or ZFS in general.  
+See also: [WD Red SMR vs CMR Tested: Avoid Red SMR](https://www.servethehome.com/wd-red-smr-vs-cmr-tested-avoid-red-smr/) and [We put Western Digital’s dreaded SMR Red drive to the test](https://arstechnica.com/gadgets/2020/06/western-digitals-smr-disks-arent-great-but-theyre-not-garbage/).  
+
+Consult your drive manufacturer, such as [Western Digital](https://support-en.wd.com/app/answers/detailweb/a_id/50697/~/steps-to-determine-if-an-internal-drive-uses-cmr-or-smr-technology) or [Seagate](https://www.seagate.com/products/cmr-smr-list/), to determine whether a disk uses CMR or SMR technology.  
+{{< /hint >}}
+
 {{< /expand >}}
 
 {{< expand "Nearline SAS Disks" "v" >}}