No, There are different forms of memory that can retain information after power is restored.
CMOS memory keeps data with a small battery.
ROM memory never changes after it has been set.
EPROM memory can be erased either by an electrical pulse or ultraviolet light.
FLASH memory can be programmed again, but is slow.
SSD is an improved form ht is faster tenn a hard drive.
There is a new form of this call M.2 and is documented below:
https://en.wikipedia.org/wiki/M.2However, general use of this new memory might take awhile.
A nice compromise is the 2.5 inch standard, which can use either a hard drive of a form of FLASH memory. Read about the 2.5 inch standard here:
2.5 inch HDD or SSD Videos 
