I recently upgraded my workstation's SSDs, so now I have 2x256GB SSDs laying around. I am considering to use them as L2ARC disks on my NAS.
However my NAS has only 12GB of RAM and 8TB worth of disk space (5x2TB in RAID-Z). I've read that having L2ARC in low end servers might hurt performance instead of improving it, because it consumes 1-2GB of ARC per 100GB of L2ARC. If this is true it would mean that 10GB of 12GB available would be wasted, right?
Another thing I've considered is using one of the SSDs as a ZIL disk. The NAS shares stuff with my workstation though NFS (over a infiniband connection). I've read that NFS will benefit greatly from having ZIL, although the share is mounted with "async" option. However I think this is a impractical approach, as 256GB is way bigger than the 1-2GB recommended.
Is there a way to create a pool of both SSDs and use part of it as ZIL and another part for L2ARC? What other solution would you recommend?
PD: The server is mainly used by me. I have both a lot of media and back-ups (Large files uncommonly accesed). And college stuff (Small files commonly used and rewritten). It rarely has some more users that access photos over WAN, so not a serious bandwidth concern.
