ARC reactor also caches?

The fictional arc reactor in Iron Man’s suit was the epitome of coolness for us geeks. In the latest edition of Oracle Magazine, Iron Man is on the cover, as well as the other 5 Avengers in a limited edition series (see below).

Just about the same time, I am reading up on the ARC (Adaptive Replacement Caching) that is adopted in ZFS. I am learning in depth of how ZFS caching works as opposed to the more popular LRU (Least Recently Used) caching algorithm that is used in most storage cache memory. Having said that, most storage vendors employed a modified LRU algorithm, with the intention to keep the most recently accessed pages in memory as long as possible. This is true in NetApp’s Data ONTAP (maybe not the ONTAP GX in which I have little experience) and EMC FlareOE. ONTAP goes further to by keeping the most frequently accessed pages permanently in memory. EMC folks would probably refer to most recently accessed as spatial locality while most frequently accessed as temporal locality.

Why is ZFS using ARC and what is ARC? (more…)