SMR or CMR for parity/data (WD Red or Gold/HGST)

[abrax]

Just planning my Unraid build and moving over from a very classic Windows primary/secondary drive solution:

 

Facts
- I have two 6TB WD Red (SMR) drives

- my current usage is just around 6TB, I'd like to add another 6TB drive to future-proof with 12TB space and a parity drive

- my usage so far is mostly media storage, so very read-heavy

 

Questions:

- I'd like to move towards CMR in the future and add a faster CMR drive as a third one; would it make any significant difference in this read-heavy setup?

- should the more reliable/faster CMR drive be placed as the primary data drive (where most of my sensitive and less sensitive data is) or as the Parity drive as it needs to do most of the writes?

- for people familiar with current WD lineup: WD Gold or WD HGST Ultrastar is the way to go? (I'm seeing prices dependeing on retailers from being the same to HGST priced some $80 more - are there differences?)

[JorgeB]

CMR is always better if possible, but SMR will work if it's mostly for reads, just expect slower performance during writes, even for large files and depending on the disks it can be 3 or 4 times slower, and if possible avoid SMR for parity, or it will be slow writing to any disk, even CMR ones.

[abrax]

Thanks! I wouldn't ditch my SMR WDs so far, so if I understand you correctly, in a 2 SMR + 1 CMR disk setup I should add the CMR as the parity disk and use SMRs as data drives?

[JorgeB]

2 minutes ago, abrax said:

in a 2 SMR + 1 CMR disk setup I should add the CMR as the parity disk and use SMRs as data drives?

Yes, so if you then add or replace a CMR data disk it won't be penalized by the SMR parity.

[abrax]

Excellent, thanks for the advise.