I always smile when my BA’s capture client requirements like “a database” and “a few users”.
Others have said it and I’ll echo that you may want to look at a managed solution from Dell, hp or Lenovo before you invest in the build. However before you even consider buy Vs build, some questions to ask the business users and exec:
Are they happy with the current software? If there are critical features it is missing now or in the near term (regulatory updates etc), would an option be to look at a holistic upgrade to a new solution that may come with hardware or even a Cloud platform.
Assuming the answer is “don’t touch it, that database must never be changed” then consider whether you should get someone else to at least host the server for you, and access remotely over secure VPN. They will do all the hard work of keeping the blinkenlights a’blinkin.
If they do insist on local hosting, then ask the question, if I lose access to this database for a day, week, month, would the business be crippled? If the answer is:
A) A day: Invest in a pair of servers and practice role swaps. Consider virtualization in a 2 node cluster so that the second server can take over seamlessly and you have capacity for other VMs that can run test instances or data warehouses. (This is likely beyond your requirements but at least ask the users before assuming they don’t want somewhere to run their big data queries)
B) A week, then enterprise hardware with 24 hour onsite replacement is a good solution. Depending on your market Dell or HP may be good options and not that expensive.
C) A month, then proceed with the build above. My only modification to your solution would be to drop the rocket raid card and just go for a HBA with software redundancy. Unless you are using more than a pair you won’t see any uplift in performance from an onboard controller. Ideally raid 10 (4 drives) or raid 6 for better drive level redundancy. You don’t mention your OS choice. If you have the option consider ZFS.
Final point assuming you continue with local build. Have you considered future growth of your business and who will maintain this infrastructure if you or your technical colleagues move on or become focussed on your firm’s pivot to AI Blockchain App development? The answer to this question is usually the one that drives most small businesses to move to PaaS or SaaS solutions and I see fewer and fewer clients, especially regulated ones like accountancy, going down the DIY route.
Sorry for the long answer. All opinions above are my own, written in general terms and should not be considered professional advice from my firm.