What should I size my ARC size to?

[allanonmage]

I've seen a rule of thumb that you should have 1GB of RAM for every 1TB of storage, and apparently it's vague on purpose due to differing usage, but probably plateaus around 64GB for most people.

In SCALE, apparently you need to set you ARC cache because reasons, and this video goes over it, and explains how to set it. How do I know what to set it to though? How much RAM does TrueNAS need for itself?

For me, right now it's using 1.7GB, and all I have turned on is SMB. It's going to be a file server and that's about it. I have 64GB of physical RAM, and I will set the ARC to 58GB for now, to leave some room for the OS if it's needed. I did search the forums a few different ways, but didn't find the answer to my question. I searched the getting started guide, and it didn't cover setting the ARC manually, but did talk about a lot of ARC things.

I saw several threads about Autotune, but didn't find any GUI elements for tuning nor AutoTune.

 

[Whattteva]

SCALE has a default max of 50% of total RAM and it is not recommended to set it higher than that. See this post for reference.

SCALE using only 50% of RAM for ZFS by default?

I am running the nightly build of Sep 9th Out of the box, no tuning A single SMB share which is receiving Data will not use more than 16 out of 32 GByte.

www.truenas.com

If you want ARC to use as much as possible, use CORE. It will use as much of your total RAM minus 1 GB out of the box safely without compromising system stability just like this screenshot below. Notice that free RAM is ~1 GiB. I did not have to do anything special for this.

 

[allanonmage]

I went with SCALE for hardware support. I am using a gamer themed motherboard, and from what I read, BSD and/or TrueNAS still doesn't include RealTek drivers because they are for plebs or something. Also, Ryzen is, mindbogglingly, also not supported on BSD.

 

[LarsR]

You can run a ryzen based build on core, i've done so for a year before scale came out.
The problem was that some power saving options, e.g. c-states and amd cool&quiet could result in system lock-ups.
As far as i remember that was resolved in bsd 13 and therefore should not be an option anymore on core 13.
The problem with realtek nics still persists though.

 

[danb35]

The problem with realtek nics still persists though.

...and it's in SCALE too, because the problem is that the hardware is garbage.