Dear Zygo,

Thank you for this fantastic message.  I hope you -- and the rest of the 
list -- doesn't mind my jumping in mid-message...

On 17/01/2021 19:55, Zygo Blaxell wrote:

You can use a NVME device as a dm-cache or bcache device--the low-latency
interface is ideal for caching use cases, if you have a suitably fast
and robust SSD.

I have about 4 enterprise grade HGST SLC 100 GB and SLC 200 GB SAS 
SSD's.  I want to use these as some kind of cache or fast tier for a NAS 
I am building.

**It has been suggested to me that I should use these SLC SAS drives 
with dm-cache, by pairing one of each of four SSD's with a corresponding 
high capacity NAS drive.**

This is for a home NAS so quietness is the major concern.  Putting the 
NAS in our living room is the only practical option _at this point in 
time_ for various reasons.

This is going to be a "pure NAS" and the chassis will be roomy.  For 
example, I already have both the following chassis and I have yet to 
choose one or the other:

-   Supermicro SC 732D4F-903B ( 
https://www.supermicro.com/en/products/chassis/tower/732/SC732D4F-903B )

-   Fractal Define XL R2 ( 
https://www.fractal-design.com/products/cases/define/define-xl-r2/black-pearl/ 
)

I think WD Red or Seagate Ironwolf drives would be best option as they 
run at 5400 RPM and keep vibration lower.  4x 8-14 TB HDD's in mirrored 
pairs (obvioulsy taken the dm-cache pair also into account).

Note to self: Investigate HDD mounting kits to absorb mechanical 
vibration.  Recommendations are welcome!

Any other suggestions would be greatly welcome!!

Andrew