Today all hard drives and SSDs have over their storage medium of RAM on their board. It serves as a buffer to speed up trade between the mass media and computer. On most hard drives today it has a capacity of 64 MB but can get into SSDs to 512 MB.
But when a power outage that memory will be erased and the data will not be written to disk. This can cause corruption and loss of information. Hard drives with little RAM the problem is less critical than the SSD in RAM that can be a significant amount of RAM. To overcome this problem the SSD manufacturers have inserted in their professional products a capacitor for powering the hard time that the contents of the RAM is copied to Flash memory, a few seconds.