The L2ARC is just a read cache that works alongside the regular ARC stored in RAM. If the L2ARC device malfunctions then you might see a performance hit, but yo

The L2ARC is just a read cache that works alongside the regular ARC stored in RAM. If the L2ARC device malfunctions then you might see a performance hit, but your pool will remain intact. All L2ARC reads are checked for integrity, so invalid data will be rejected and read from the pool directly instead. ZFS can even tolerate the loss of a SLOG device as long as A) the SLOG is not currently being read to rebuild after a crash and B) all writes that occurred before the SLOG was lost have been fully flushed to the pool disks.