Cache protected PCI controllers

Cache protection

— function used in some advanced RAID controllers (see "Type") to protect against power failures.

Recall that when exchanging information through a RAID controller, this information is first written to the controller's cache, and then transferred "as intended". And since the cache uses volatile memory, when the power is turned off, all its contents disappear. This can lead to data corruption, sometimes quite significant.

Cache protection helps to avoid such troubles. It is usually implemented as follows: in addition to the actual cache, a non-volatile flash drive (NAND) is installed in the controller, as well as a supercapacitor that plays the role of a backup energy source. And if the main power fails, the information from the cache is rewritten to non-volatile memory (the energy of the supercapacitor is usually enough for such an operation with a margin) and is stored until the next power-on.

Thus, this feature in RAID arrays minimizes the possibility of data corruption due to power outages. The disadvantage of classic cache-protected controllers is their high cost.