CompactFlash type of storage, usually solid-state using flash memory, It looks to the system like an IDE drive. When based on flash memory it has a limited number or erase cycles, usually on the order of 100,000. If one were to write the same block over and over, once a second, the memory would fail in a little over a day, once a minute over two months, once an hour, 11.4 years.
Since few CF vendors list the erase cycle lifetime of their cards this is an estimate based on the fact that at least one such device exists. Reports of devices with 1M cycles exist.