Instead of labeling 20 external hard drives and keeping them in a secure location, it may be a better option to build your own Network Attached Storage (NAS).
Network Attached Storage (NAS) is simply a storage device that is attached to your home or office network, either through cables or wireless. It allows for all connected devices with correct permissions set to access files on internal drives. It's possible to purchase a prebuilt NAS, but the prices can get out of hand depending on requirements and features. It's cheaper to go it alone.
Why you should buy a NAS
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