A
ramdisk is a
virtual block device created in
RAM upon which a
filesystem is created.
Ramdisks are most often used in
operating system installers and applications where a small volatile filesystem is not a limitation (
ex.
Coyote Linux,
BlessTiVo).
One side effect is that file accesses to a ramdisk are far faster than to a electromechanical disk. The latencies for ramdisks are minimal and random seek penalties are nonexistant. Some specialized applications use a dedicated hardware ramdisk to exploit this phenomenon. Supercomputers sometimes use them for increased speed in reading and writing data sets while many high-end hardware RAID systems use them as a write-back cache to reduce the RAID 5 write penalty.