Disk tiering on Edge servers

We have been deploying more Edge servers recently on different locations. Some of them have SSDs some have HDD. Of course the ones with SSDs are on busier locations.

We wanted to improve its efficiency being able to add HDDs to these Edge servers so it can cache a lot more content and Nginx could put the more requested objects on SSD and of course the the less in the HDD.

In that way things can be simplified with less Edge servers but more powerfull.

If you are not willing to develop this logic inside the Edge server with tiering with Nginx object placement, perhaps something that direct requests to certain Edges that it knows has SSD instead of the ones it knows has HDDs. Problem here is the CDN to do based on popularity of the object.