Because hardware failure is always possible, and portable drives are often small enough to lose or leave behind by accident. Portable SSDs are better here, but you should still keep your irreplacable data backed up on a desktop drive and / or on a cloud service.
Don’t Use a Portable Hard Drive as Your Only Backup. Portable hard drives are made up of spinning glass or metal platters, making them a poor choice as a primary backup of your data-especially if you carry them around.But if you need cavernous amounts of external storage, a hard drive is a better option for most, as multi-terabyte external SSDs sell for several hundred dollars, but 4TB portable hard drives can sell for under $100 (£90). A portable SSD will also be much faster at reading and writing lots of data.
If you don’t need terabytes of storage and you often travel with your drive, a portable SSD is worth paying extra for. But they’re also much slower and more fragile than solid-state drives. When shopping for an external drive or SSD, consider the following:
