ARC / L2ARC(Adaptive Replacement Cache)
ZFS's in-RAM read cache (ARC), optionally extended onto an SSD as L2ARC.
ARC makes ZFS feel fast by caching frequently used data in memory — which is why ZFS loves RAM. L2ARC on an SSD helps only specific workloads and still consumes RAM to index, so add it deliberately.
Related articles
ZFS
An advanced filesystem and volume manager offering data integrity, snapshots, compression and software RAID.
ECC RAM(Error-Correcting Code Memory)
Memory that detects and corrects single-bit errors, improving data integrity on always-on servers.
SSD(Solid-State Drive)
Flash-based storage with no moving parts, far faster and quieter than a hard drive.