How important is the CPU for ZFS?

I want to build a truenas server with the cheapest CPU I can find that can support ECC RAM: Celeron G4900T + 64gb ECC RAM + 4x18 TB SAS drives.

I don't have experience with ZFS or with truenas (core or scale), how much important is the CPU?

Use case: hundreds of thousands of small files mostly under 1 mb, but just 2-3 concurrent users

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reason why i use a C246 motherboard and other high end expensive components, but such a cheap cpu: someone will sell me used supermicro mobo+ECC ram+SAS HDDs for 500 euro, but no CPU. A Celeron G4900T costs like 15 euro, i was wondering if it could suffice, because this is already overkill for me, at the moment i have no idea on how to use the 36 TB of storage (2x redundancy)
You don't mention your performance requirements and I'm unfamiliar with that CPU. Are you trying to saturate your 1G presumably NIC? Reads or writes?
- No, just thousands of small files. Windows takes around a minute to enumerate all the files in the main share via SMB
  
  @Moonrise2473
  That looks more like ARC problem, it can hold a large index of the filesystem if you give it enough room in ram, avoiding the need to seek thousands of files on a spinning disk, which takes time. HDDs are fine for sequential operations, Random IO, which is your usecase, is their biggest weakness.
  @eleitl
  
  You should be good, then. Probably don't need SSDs for ZIL and L2RC either. Don't forget to schedule a weekly scrub, to catch bit rot. Essential for large drives.
It’s ok until you start using jails or dedup.
ZFS tends to be more RAM intensive so make certain you have, at bare minimum around 16GB. But I would push for more.
In my (admittedly) limited experience with ZFS, it utilizes more RAM than CPU except for scrubs.

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