If you look around this subforum (using the forum search feature - magnifying glass icon upper right) you’ll find a number of people who have put larger hard drives in their single bay My Cloud units. Don’t think anyone yet has reported back with an issue on very large drives.
At some point however, for most people, it becomes a waste of money and effort to put an expensive hard drive into a limited NAS enclosure like the first gen My Cloud that is no longer supported by WD. Outside of certain specific desires, one would ultimately be better off buying a more capable NAS enclosure to put a large expensive hard drive(s) into.
For example, my post a while back where I experimented using a 12TB drive in a first gen single bay My Cloud and attaching a second 12TB as an external drive for a total of 22TB’s of usable storage space. Worked fine for the experiment. Put those two 12TB drives into a Synology unit instead.
Another post where i put a 8TB WD Red into a first gen single bay My Cloud.
And another thread where I experimented with using a 2.5 inch hard drive in a single bay My Cloud. Strangly I couldn’t get an SSD drive to work, but a HDD (mechanical) worked fine if a bit slow.
Another user started a recent thread where using 18TB is pondered. Don’t know if they ever followed through before the thread got derailed.
The difference is different hardware inside (processor and RAM). Which lead to having different firmware. Someone a long time ago put together a chart listing the hardware/RAM of various My Cloud units: http://wdstagingsplit.staged-by-discourse.com/t/my-cloud-model-reference/203498
Model: My Cloud (Gen 1)
Code: SQ - Sequoia
Specs: Mindspeed Comcerto 2000 M86261G-12 Dual Core 650 MHz, 256 MB RAM
Note: Part Number: WDBCTLxxxxHWT-00. Firmware 03.xx.xx and 04.xx.xx
Note: Firmware 03.xx.xx has 4K pages and firmware 04.xx.xx has 64K pages.Model: My Cloud (Gen 2)
Code: GLCR - Glacier
Specs: Marvell Armada A375 Dual Core 1.0 GHz, 512 MB RAM
Note: Part Number: WDBCTLxxxxHWT-10. Firmware 02.xx.xx
Because of the firmware numbering, and the difference between the two units many are confused. WD further confused things by introducing the My Cloud Home line which many mistook for being similar to the My Cloud line, it isn’t. The Home devices have a different operating system and different features. Its a confusing mess for the customers.
The second gen single bay My Cloud is barely capable of running OS5 v5.x firmware. Read through the MANY complaints in the OS5 subforum about second gen single bay users who’s units were unusable after updating to OS5. They had to stop features like Twonky and Remote Access to regain usage of their devices. First gen single bay with even less capable hardware than the second gen has been end of software updates for several years now anyhow.
