In 2006, IBM was granted a patent for the adaptive replacement cache policy.
ARC improves the basic LRU strategy by splitting the cache directory into two lists, T1 and T2, for recently and frequently referenced entries.
These ghost lists act as scorecards by keeping track of the history of recently evicted cache entries, and the algorithm uses ghost hits to adapt to recent change in resource usage.
If no free space exists in the cache, this marker also determines whether either T1 or T2 will evict an entry.
Sun Microsystems's scalable file system ZFS uses a variant[3] of ARC as an alternative to the traditional Solaris filesystem page cache in virtual memory.
If a SSD is set up to store the second level disk cache, it is called an L2ARC.