To put some numbers on that, FreeBSD recommend 1Gb as a minimum, and you can tune to run stably in less. Dedup is <i>insanely</i> greedy - FreeBSD handbook reckons on 5GB &#x2F; TiB in practice, rather than the 2GB often stated.  99 out 100 times you&#x27;re better off using compression anyway.<p>All you&#x27;re really losing is the caching, which may not be so important for what is going to be mostly writes in this backup app.<p>If you want to add some cache headroom to a Pi, you could add a USB stick to the pool as cache.  I just threw RAM at my homebuilt NAS, so I can&#x27;t say how helpful this is.  I imagine it&#x27;s useless for sequential and pretty good for small random access reads, directories etc.