Why does the TrueNAS created by proxmox occupy pre-allocated memory?

[vrsaoc]

I created TrueNAS through proxmox. Since I created it, it has been occupying my pre-allocated memory space. I would like to know how to make TrueNAS use memory dynamically?

system version：TrueNAS-SCALE-22.12.3.2

 

[Arwen]

TrueNAS uses ZFS, and ZFS will use memory for a type of read cache call ARC, (Adaptive Replacement Cache). For TrueNAS SCALE, that is maxed at 50% of memory. Then their is the actual code and other data installed into memory.

Reducing the ARC means more reads from disks, and potentially slower performance.

Neither TrueNAS nor ZFS were designed to be virtualized. Lots of people do it, and their are now guides to make it reasonably reliable. But, wanting a smaller memory foot print implies you want less ZFS ARC.

Next, 8GB is very low for TrueNAS, some might even consider it too low. Today, many advocate for 16GBs as the recommended minimum. (I don't know the "official" required minimum... you should be able to get that off the documentation.)

 

[Whattteva]

(I don't know the "official" required minimum... you should be able to get that off the documentation.)

According to this doc, 8 GB.

CORE Hardware Guide

Describes the hardware specifications and system component recommendations for custom TrueNAS CORE deployment.

www.truenas.com

 

[vrsaoc]

TrueNAS uses ZFS, and ZFS will use memory for a type of read cache call ARC, (Adaptive Replacement Cache). For TrueNAS SCALE, that is maxed at 50% of memory. Then their is the actual code and other data installed into memory.

Reducing the ARC means more reads from disks, and potentially slower performance.

Neither TrueNAS nor ZFS were designed to be virtualized. Lots of people do it, and their are now guides to make it reasonably reliable. But, wanting a smaller memory foot print implies you want less ZFS ARC.

Next, 8GB is very low for TrueNAS, some might even consider it too low. Today, many advocate for 16GBs as the recommended minimum. (I don't know the "official" required minimum... you should be able to get that off the documentation.)

Ok, thank you for your answer, can't I achieve the effect I want by adjusting ZFS?

 

[vrsaoc]

According to this doc, 8 GB.

CORE Hardware Guide

Describes the hardware specifications and system component recommendations for custom TrueNAS CORE deployment.

www.truenas.com

Your performance is so strong, I just use it as a nas to store my files and videos

 

[Arwen]

Ok, thank you for your answer, can't I achieve the effect I want by adjusting ZFS?

That is the point. You can adjust ZFS tunables to get different results with specific consequences. But, anything out of the ordinary, like running TrueNAS as a VM, is for you to decide what tunables to change.

Now if you want the specific tunable to change the ZFS ARC maximum for TrueNAS SCALE, then perhaps someone else can help you with what it is, and how to change it. I don't know it, just that there is a limit.


A lot of ZFS and TrueNAS that is beyond the straight forward questions, does require research. Neither ZFS nor TrueNAS are the easiest to learn whence you get beyond common installations or use cases. That is not meant to stop someone from using TrueNAS, just as a fact.

Good luck.