a cache drive is l2arc. Brendan Gregg&#x27;s post[0] explains it well, but the TLDR is that l2arc is very much like an l2 cache in a cpu. Recent and relevant items are held on a fast drive in case it will be needed in the near future. It is really an L2 cache: L1 is called ARC and is held in dram.<p>If I recall correctly, the extra indexes and tags mean l2arc requires more memory to work efficiently.<p>[0]: <a href="https:&#x2F;&#x2F;blogs.oracle.com&#x2F;brendan&#x2F;entry&#x2F;test" rel="nofollow">https:&#x2F;&#x2F;blogs.oracle.com&#x2F;brendan&#x2F;entry&#x2F;test</a>