Trying to decide if I diy or purchase

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Considering your situation, given the budget and the need for 8 to 16TB storage for your photography business, you could explore building a NAS yourself using Unraid. This approach offers more flexibility and control over the hardware configuration. While Asustor and Terramaster may have more budget-friendly options, their operating systems might be less robust compared to Unraid. Building your NAS allows you to tailor it to your specific needs, ensuring longevity and adaptability to future requirements. If you choose to go with a pre-built solution, be sure to check if Asustor or Terramaster support Unraid installations. For more guidance, you can also use the NAS Finder Tool at NAS Builder to explore additional options based on your preferences.
https://nascompares.com/nas-builder/