Creating IT infrastructure is a huge responsibility and their is ALOT to hardware purchases and investments. If you are not sure about what to get, get in touch with a trusted vendor that can help you out and ask questions.
The major difference in storage is
Their are pros and cons to everything, so research which one of these would benefit you the most.
From my experience 2.5” disks, normally dont have any shielding on the backplate which make them more susceptible to corrosion, even in heat controlled environments if their is some moisture in the air such as an office. 1.5” drives (for what ever reason) normally have backplate shielding, and SSD’s always have shielding since the memory that makes up the SSD is encapsulated entirely.
Their are many areas that goes into storage investments, but the two major ones are probably.
Durability vs price.
Lower price normally means that the disks are less durable over long periods of times (years), which can be a good or bad thing based on your infrastructure. For example, Google only use cheap disks and hardware for their own storage solutions because it’s overall cheaper.
Their are different ways to build your storage solution in regards to raid. If you are building a serious solution i would advice looking into ZFS. Else software raid might do the job for you. Personally i would put ALOT of thought into if i ever were to decide between software and hardware raid, since hardware raid is a dinosaur in many areas. Example, many controllers dont allow you to flash the configuration, so if the controller dies the entire raid dies.
Than their is speed, write block size, storage write method, cache?, long-term-storage?, backup? with more.
Also some drives are really expensive because of the firmware that can give you disk health stats for your particular server and setup, but you can also get cheap drives from almost any vendor and place in your storage, this will just omit the health stats.
It’s very few things that dictate if you are going to spend $10.000 or $4.000 on a solution.
Again you can also ask a vendor to create an entire solution for you on the hardware side, based on your requirements and than setup the storage yourself.