45HL has repeatedly said thay have no intent to release something bigger than 15 HDDs for the prosumer market. You would need to engage the enterprise side for that. If you can’t go with bigger drives your options would seem to be:
- Get a quote from 45Drives on a Q30. See if they’ll quote you a price for just the chassis. It’ll be expensive, but you’ve defined your needs.
- Look for a used Q30/S45/XL60 on eBay. These come up occasionally and I think there are currently 2 or 3 listed. You have to be careful about the generation though depending on your use case.
- Get a 24 or 36 drive used Supermicro chassis off of eBay. It’ll be noisy.
- Look into external JBODs like ones from NetApp, again likely off of eBay
- Look into building this external shelf project someone posted on YouTube;
A Disk Shelf Project - Look into buying a second HL15 chassis-only and setting it up as a JBOD like I did for a while when I was creating a backup server;
HL15 Tinman Simple JBOD Expansion
Finally, you might want to analyze your usage pattern, Do you really need 360TB+ all online in the same box? You could probably just buy a second HL15 and partition your workload across the two. For example, I have my personal media on one, and my professional stuff on the other. With an external JBOD you have to be a bit careful to not corrupt your ZFS pool(s).